Encoding device, decoding device, and data structure

ABSTRACT

A video encoding device includes a side information determination section and a side information encoding section. The side information determination section sets a quantization parameter for each macroblock in such a manner that a difference between quantization parameters for each pair of macroblocks with successive encoding orders is equal to one of n difference values, and transforms the difference into one of n indices with respect to each pair. The side information encoding section generates a binary sequence having a length corresponding to the size of the absolute value of the index. The total of absolute values of the n indices is smaller than the total of absolute values of the n difference values.

TECHNICAL FIELD

The present invention relates to an encoding device for generatingencoded data by encoding an image. Further, the present inventionrelates to a decoding device for decoding the encoded data generated byuse of such an encoding device.

BACKGROUND ART

Video encoding devices have been used for efficiently transmitting orrecording videos. Examples of a specific video encoding method encompassH.264/MPEG-4 AVC (hereinafter abbreviated as H264/AVC) (described in NonPatent Literature 1) and a method employed in KTA software which is ajoint development codec in VCEG (Video Coding Expert Group).

According to such an encoding method, an image (picture) constituting avideo is managed in a hierarchical structure which is constituted by (i)a plurality of slices into which the image is divided, (ii) a pluralityof macroblocks into which each of the plurality of slices is divided,(iii) a plurality of sub blocks into which each of the plurality ofmacroblocks is divided, and (iv) a plurality of blocks into which eachof the plurality of macroblocks or the plurality of sub blocks isdivided.

A video encoding device based on H264/AVC (1) subjects an image to DCTtransform, (2) quantizes a frequency component obtained by the DCTtransform (Discrete Cosine Transform), and (3) variable-length-codes thequantized frequency component, thereby obtaining an encoded image.Quantization step employed in quantization is variable with respect toeach macroblock, and the video encoding device is designed to encode aquantization parameter that designates the size of the quantization stepand to supply the encoded quantization parameter as well as the encodedimage to a video decoding device.

The process for encoding the quantization parameter is detailed belowwith reference to (a) of FIG. 7, FIG. 11, and FIG. 12.

(a) of FIG. 7 is a view schematically showing a slice constituted bymacroblocks MB1 to MBn. FIG. 12 is a view showing examples of differencevalues of quantization parameters assigned to the macroblocks MB1 toMBn. FIG. 11 is a table showing relations among difference values ofquantization parameters, code numbers, and binary sequences outputtedwhen binarizing the code numbers.

As shown in FIG. 12, the video encoding device determines, with respectto each picture, a default value pic_init_qp of a quantization parameterof the picture (hereinafter “picture default QP value”). Furthermore,the video encoding device determines, with respect to each sliceincluded in the picture, a default value (SliceQP_(Y)) of a quantizationparameter of the slice (hereinafter “slice default QP value”).Furthermore, the video encoding device determines, with respect to eachslice, a difference value slice_qp_delta obtained by subtracting, fromthe slice default QP value of the slice, the picture default QP value ofthe picture including the slice.

Furthermore, the video encoding device determines, with respect to eachmacroblock MBi (i=1−n) included in each slice, a quantization parameterQP_(Y) in raster scan order, and determines, as a QP difference value ofa macroblock MBi, a difference value mb_qp_delta (hereinafter “QPdifference value”) obtained by subtracting, from the determinedquantization parameter, a quantization parameter of a macroblock MBi−1previous by one to the macroblock MBi in raster scan order. It should benoted that a QP difference value mb_qp_delta of a first macroblock MB1in raster scan order is obtained by subtracting, from a quantizationparameter determined with respect to the macroblock MB1, a slice defaultQP value SliceQP_(Y) of a slice including the macroblock MB1.

The video encoding device binarizes, based on the table shown in FIG.11, the QP difference value mb_qp_delta generated as above. That is, theQP difference value is transformed, when the absolute value thereof isn, into a binary sequence whose length is 2n or 2n+1 by unarybinarization.

Processes carried out by such a video encoding device and such a videodecoding device have advantages below.

That is, 1) the amount of codes of an encoded image (main information)can be reduced efficiently without impairing subjective image quality ofa decoded image decoded by a video decoding device, and 2) by regulatinga quantization parameter suitably, the amount of codes of an encodedimage with respect to each frame can be kept at a desired rate.

Furthermore, 3) by quantizing an image treated later as a referenceimage by a smaller quantization step, it is possible to reduce an amountof codes in prediction residual that is generated later, and thus toreduce an amount of codes in a video image as a whole, and 4) byregulating the amount of a quantization parameter so that RD (ratedistortion) cost is small, an encoding efficiency can be increased.

CITATION LIST Non-Patent Literature

-   Non-Patent Literature 1-   ITU-T Recommendation H.264 (03/2009)

SUMMARY OF INVENTION Technical Problem

However, although the above configuration allows reducing the amount ofcodes of an encoded image (main information), the amount of codes of aQP difference value supplied as side information together with the maininformation to the video decoding device is not sufficiently reduced.For example, in some cases, the amount of codes of a QP difference valueoccupies approximately 10% of the whole encoded data supplied to a videodecoding device. This is because the amount of codes of a QP differencevalue is in relation to the absolute value of the QP difference value asis seen from FIG. 11.

The present invention was made in view of the foregoing problem. A mainobject of the present invention is to realize an encoding device capableof reducing the amount of codes of a quantization parameter supplied toa decoding device compared with a conventional art, and a decodingdevice capable of inverse-quantization based on a quantization parametersupplied from such an encoding device.

Solution to Problem

In order to solve the foregoing problem, an encoding device of thepresent invention is an encoding device for quantizing, in accordancewith a value of a quantization parameter, an image in each of aplurality of unit regions constituting an input image to be encoded, theencoding device comprising: setting means for setting a quantizationparameter used in encoding each unit region, the setting means settingan quantization parameter for each unit region in such a manner that adifference between a quantization parameter for a unit region and apredetermined reference value is equal to one of n predetermineddifference values; transform means for transforming, with respect toeach unit region, the difference between the quantization parameter forthe unit region and the predetermined reference value into an integer inaccordance with a transform rule by which the n difference values aretransformed into n number of integers, respectively; and binary sequencegeneration means for generating a binary sequence having a lengthcorresponding to a size of an absolute value of the integer into whichthe difference is transformed by the transform means, a total ofabsolute values of the n integers being smaller than a total of absolutevalues of the n difference values.

A conventional encoding device is designed to generate a binary sequencehaving a length corresponding to the size of an absolute value of adifference between quantization parameters with respect to each unitregion.

In contrast thereto, in the encoding device of the present invention, adifference between quantization parameters in each unit region istransformed into an integer, and a binary sequence having a lengthcorresponding to the size of the absolute value of the integer isgenerated. Furthermore, since the total of the absolute values of the nintegers is smaller than the total of the absolute values of the ndifference values serving as candidates for the difference between thequantization parameters, the absolute value of the integer obtained bythe transform is statistically smaller than the absolute value of thedifference value to be transformed.

Consequently, the binary sequence generated from the difference betweenthe quantization parameters has a smaller length in the encoding deviceof the present invention than in the conventional encoding device. Thisyields an effect of further reducing an amount of codes of quantizationparameters supplied to a decoding device, compared with the conventionalart.

In order to solve the foregoing problem, a decoding device of thepresent invention is a decoding device for decoding encoded data to setquantization parameters regarding unit regions constituting a decodedimage, the decoding device comprising: extraction means for extractingdata of binary sequences regarding the unit regions from the encodeddata; integer generation means for generating integers corresponding tolengths of the binary sequences regarding the unit regions from the dataof binary sequences extracted by the extraction means; and specifyingmeans for specifying, according to information in which n integers arerelated to n difference values regarding quantization parameters,respectively, difference values for the unit regions based on integersfor the unit regions that are generated by the integer generation means,the quantization parameters for the unit regions being generated basedon the difference values specified by the specifying means.

With the arrangement, when receiving encoded data including the binarysequence from the encoding device of the present invention, the decodingdevice of the present invention can appropriately specify differencevalues regarding individual unit regions based on the encoded data. Thatis, the decoding device of the present invention can suitably specifyquantization parameters regarding individual unit regions supplied fromthe encoding device of the present invention.

Therefore, the decoding device of the present invention can carry outinverse-quantization based on quantization parameters supplied from theencoding device of the present invention.

Furthermore, in order to solve the foregoing problem, an encoding deviceof the present invention is an encoding device for quantizing, inaccordance with a value of a quantization parameter, an image in each ofa plurality of unit regions constituting an input image to be encoded,the encoding device comprising: selection means for selecting, in apredetermined order, a plurality of third unit regions constituting eachof the plurality of unit regions; determination means for determining adifference value of a quantization parameter for one of third unitregions to be quantized in each of the plurality of unit regions, saidone of third unit regions being firstly selected by the selection means;and calculation means for calculating the value of the quantizationparameter to be referred to when quantizing images in the third unitregions to be quantized in each of the plurality of unit regions, thevalue of the quantization parameter being calculated based on thedifference value of the quantization parameter for the unit region whichis determined by the determination means. Here, “quantizing an image”may be one of quantizing a residual image between an input image and apredicted image and quantizing a transform coefficient obtained byfrequency-transforming a residual image.

With the arrangement, the encoding device of the present inventiondetermines a difference value of a quantization parameter for one thirdunit region selected from each unit region, and using the differencevalue of the quantization parameter, determines a quantization parameterof the third unit region to be quantized. In contrast thereto, anencoding device without the above features determines a quantizationparameter for each third unit region to be quantized, and using thequantization parameter for each third unit region, determines adifference value of the quantization parameter for the third unitregion.

That is, in order that a decoding device carries outinverse-quantization, the encoding device of the present invention isonly required to determine one difference value of a quantizationparameter per unit region and transmit the difference value to thedecoding device, whereas an encoding device without the above featuresis required to transmit difference values of quantization parameters forindividual third unit regions included in one unit region to thedecoding device.

Therefore, the encoding device of the present invention can furtherreduce an amount of codes of a quantization parameter, compared with theconventional art.

A decoding device of the present invention is a decoding device fordecoding encoded data to set quantization parameters regarding unitregions constituting a decoded image, the decoding device comprising:selection means for selecting, in a predetermined order, a plurality ofthird unit regions constituting each of the unit regions constitutingthe decoded image; reading means for reading, from the encoded data, adifference value of a quantization parameter for one of third unitregions to be inverse-quantized in each of the unit regions constitutingthe decoded image, said one of third unit regions being firstly selectedby the selection means; and specifying means for specifying a value ofthe quantization parameter to be referred to when a quantization imagein each third unit region to be inverse-quantized in each of the unitregions constituting the decoded image, the specifying being made basedon the difference value of the quantization parameter read out in saideach of the unit regions by the reading means. The quantization imageis, for example, an image on a frequency domain constituted by quantizedDCT coefficients decoded from encoded data. By subjecting thequantization image to inverse-quantization and inverse-frequencytransformation, it is possible to obtain a decoded image on a spatialdomain.

With the arrangement, the decoding device of the present invention readsout a difference value of a quantization parameter in one third unitregion selected from each unit region, and using the difference value,determines quantization parameters for individual third unit regions tobe inverse-quantized in the unit region.

In contrast thereto, a decoding device without the above features readsout difference values of quantization parameters from individual thirdunit regions to be inverse-quantized in each unit region, and using theread out difference values, determines quantization parameters forindividual third unit regions to be inverse-quantized in the unitregion.

Therefore, the decoding device of the present invention can specify,with a smaller load, quantization parameters to be used ininverse-quantization.

Advantageous Effects of Invention

As described above, the encoding device of the present invention canreduce an amount of codes in a quantization parameter to be supplied toa decoding device, compared with the conventional art. Furthermore, thedecoding device can carry out inverse-quantization based on thequantization parameter supplied from such an encoding device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a video encodingdevice in accordance with an embodiment.

FIG. 2 is a flowchart showing operations of a side informationgeneration section and a side information encoding section that areincluded in the video encoding device in accordance with the embodiment.

FIG. 3 is a flowchart showing another operations of the side informationgeneration section and the side information encoding section that areincluded in the video encoding device in accordance with the embodiment.

FIG. 4 is a block diagram showing a configuration of a video decodingdevice in accordance with the embodiment.

FIG. 5 is a block diagram showing operations of a side informationdecoding section and an MB setting section that are included in thevideo decoding device in accordance with the embodiment.

FIG. 6 is a block diagram showing another operations of the sideinformation decoding section and the MB setting section that areincluded in the video decoding device in accordance with the embodiment.

FIGS. 7( a) and (b) of FIG. 7 schematically show configurations ofslices, respectively.

FIGS. 8( a) to (e) of FIG. 8 show specific examples of a QP differencevalue table.

FIGS. 9( a) of FIG. 9 shows relations among values of indices, codenumbers serving as inputs for unary binarization, and binary sequencesserving as outputs from unary binarization. (b) of FIG. 9 showsrelations among values of indices and binary sequences serving asoutputs from fixed-length binarization.

FIGS. 10( a) and (b) of FIG. 10 show examples of amount of codes inencoding a QP difference value table.

FIG. 11 is a view of a conventional art, showing relations among QPdifference values, code numbers serving as inputs for unarybinarization, and binary sequences serving as outputs from unarybinarization.

FIG. 12 is a view showing an example of a picture default QP value setwith respect to each picture, a slice default QP value set with respectto each slice, and a QP value and a QP difference value that are setwith respect to each macroblock.

FIG. 13 is a view hierarchically showing individual information includedin side information.

FIG. 14 is a block diagram showing a configuration of a video decodingdevice in accordance with another embodiment.

FIG. 15 is a block diagram showing a configuration of a video encodingdevice in accordance with another embodiment.

FIG. 16 is a view showing an example of a picture parameter set.

FIG. 17 is a view schematically showing positions of CUs whose QPdifference values are encoded in QP encoding unit regions.

FIG. 18 is a view showing an example of coding_unit syntax. (a) of FIG.18 shows a former part of syntax. (b) of FIG. 18 shows a latter part ofthe syntax.

FIG. 19 is a view showing another example of coding_unit syntax. (a) ofFIG. 19 shows a former part of syntax. (b) of FIG. 19 shows a latterpart of the syntax.

FIG. 20 is a view showing another example of coding_unit syntax. (a) ofFIG. 20 shows a former part of syntax. (b) of FIG. 20 shows a latterpart of the syntax.

FIG. 21 is a view showing an example of transform_tree syntax.

FIG. 22 is a block diagram showing a configuration of a video encodingdevice in accordance with another embodiment.

FIG. 23 is a view showing another example of transform_tree syntax.

FIG. 24 is a view showing another example of transform_tree syntax.

FIG. 25 is a block diagram showing a configuration of a video decodingdevice in accordance with another embodiment.

FIG. 26 is a block diagram showing a configuration of a video encodingdevice in accordance with another embodiment.

FIG. 27 is a view showing another example of coding_unit syntax. (a) ofFIG. 27 shows a former part of syntax. (b) of FIG. 27 shows a latterpart of the syntax.

FIG. 28 is a view showing another example of coding_unit syntax. (a) ofFIG. 28 shows a former part of syntax. (b) of FIG. 28 shows a latterpart of the syntax.

FIG. 29 is a block diagram showing a configuration of a video decodingdevice in accordance with another embodiment.

FIG. 30 is a block diagram showing a configuration of a video encodingdevice in accordance with another embodiment.

FIG. 31 is a view showing another example of coding_unit syntax. (a) ofFIG. 31 shows a former part of syntax. (b) of FIG. 31 shows a latterpart of the syntax.

FIG. 32 is a block diagram showing a configuration of a video decodingdevice in accordance with another embodiment.

FIG. 33 is a block diagram showing a configuration of a video encodingdevice in accordance with another embodiment.

FIG. 34 is a view showing another example of coding_unit syntax. (a) ofFIG. 34 shows a former part of syntax. (b) of FIG. 34 shows a latterpart of the syntax.

FIG. 35 is a block diagram showing a configuration of a video decodingdevice in accordance with another embodiment.

FIG. 36 is a block diagram showing a configuration of a video encodingdevice in accordance with another embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment (Video Encoding Device)

The following explains a video encoding device (encoding device) 2 inaccordance with the present embodiment with reference to FIGS. 1-3,6-10, and 12. FIG. 1 is a block diagram showing a configuration of thevideo encoding device 2. As shown in FIG. 1, the video encoding device 2includes a side information determination section 21, a side informationencoding section 22, an MB setting section 23, an MB encoding section24, a variable-length code multiplexing section 25, an MB decodingsection 26, and a frame memory 27.

Schematically, the video encoding device 2 encodes an input image #100to generate encoded data #1 and outputs the encoded data #1. The videoencoding device 2 is a video encoding device partially using thetechnique employed in H264/AVC standard.

A process of encoding the input image #100 includes DCT, quantizationetc. The video encoding device 2 carries out a quantization process bychanging a quantization level with respect to each macroblock(quantization unit region).

The side information determination section 21 determines sideinformation based on the input image #100, and outputs the determinedside information as side information #21. The side information #21 issupplied to the side information encoding section 22 as well as inputtedto the MB setting section 23. The side information #21 includes apicture parameter set which is a set of parameters regarding the inputimage #100, a slice header which is header information with respect toeach slice included in the input image #100, a macroblock layer which isa set of parameters with respect to each block included in a slice, andthe like. Each of the picture parameter set and the slice headerincludes a picture default QP value and a difference value between aslice default QP value and the picture default QP value.

Furthermore, the side information determination section 21 determines,with respect to each slice, a set of QP difference values for limitingQP values assignable to macroblocks included in the slice. That is, QPvalues assignable to the macroblock MBi included in the slice arelimited so that QP difference values between the QP values assignable tothe macroblock MBi and the QP value assigned to the macroblock MBi−1included in the same slice are included in the set of the QP differencevalues.

Furthermore, the side information determination section 21 generates,with respect to each slice (table generation unit region), a QPdifference value table regarding the slice, and incorporates thegenerated QP difference value table into a corresponding slice header.The QP difference value table regarding the slice is a table generatedby relating indices indicative of individual QP difference valuesincluded in the set of the QP difference values (the indices aredifferent integers for individual QP difference values) to thoseindividual QP difference values. Alternatively, the QP difference valuetable may be one for encoding rules for generating a QP difference valuetable, as described later in the section (Additional matter 3).Alternatively, the present invention may be arranged such that a videoencoding device and a video decoding device each include a plurality ofpredetermined QP difference value tables, and indices for switching theQP difference value tables are encoded. The side informationdetermination section 21 incorporates, into a macroblock layer, an indexindicative of a QP difference value between a QP value assigned to amacroblock MBi and a QP value assigned to a macroblock MBi−1. How theside information determination section 21 determines the set of the QPdifference values and how the side information determination section 21generates the QP difference value table are described later.

The side information encoding section 22 encodes the side information#21, and outputs encoded side information #22. The encoded sideinformation #22 is supplied to the variable-length code multiplexingsection 25.

The MB setting section 23 divides the input image #100 into a pluralityof slices based on the side information #21, and divides each slice intoa plurality of macroblocks, and outputs macroblock images #23 regardingindividual macroblocks. The MB setting section 23 calculates values ofquantization parameters (QP values) regarding the individual macroblockimages #23 based on the side information #21 (this calculation will bedetailed later). Then, the individual macroblock images #23 aresequentially supplied together with the calculated QP values to the MBencoding section 24.

The MB encoding section 24 generates MB encoded data #24 with respect toeach of the sequentially inputted macroblock images #23, and suppliesthe MB encoded data #24 to the variable-length code multiplexing section25. The MB encoding section 24 generates the MB encoded data #24specifically as follows.

That is, the MB encoding section 24 subjects individual blocksconstituting the macroblock image #23 to DCT, and quantizes DCTcoefficients of individual blocks at quantization levels based on the QPvalues supplied together with the macroblock image #23. Then, the MBencoding section 24 subjects the data obtained by quantization to avariable-length encoding process so as to generate the MB encoded data#24.

The variable-length code multiplexing section 25 multiplexes the encodedside information #22 with the MB encoded data #24 to generate encodeddata #1 and outputs the generated encoded data #1.

The MB decoding section 26 sequentially decodes the MB encoded data #24corresponding to the inputted individual macroblocks so as to generatedecoded images #26 corresponding to the individual macroblocks, andoutputs the generated decoded images #26. The decoded images #26 aresupplied to the frame memory 27.

The inputted decoded images #26 are stored in the frame memory 27. Atthe time of encoding a certain macroblock, decoded images correspondingto all macroblocks prior in raster scan order to the certain macroblockare stored in the frame memory 27.

(How to Determine Set of QP Difference Values and how to Generate QPDifference Value Table)

The method by which the side information determination section 21determines the set of QP difference values for limiting QP valuesassignable to macroblocks may be any method. Specific examples thereofare as follows.

Example 1

Determine the set of QP difference values in which each QP differencevalue is factor* (−1)^(j+1)*Ceil(j/2) (j=1, 2, . . . ).

Example 2

Determine the set of QP difference values in which each QP differencevalue is 0 or (−1)^(j+1)*factor^({Ceil(j/2)−1}) (j=1, 2, . . . ).

Example 3

Determine the set of QP difference values in which each QP differencevalue is 0, 1, −1, or factor*(−1)^(j+1)*Ceil(j/2)+3 (j=3, 4, . . . ).

In any of the Examples 1 to 3 above, a slice type is judged with respectto each slice, and when the slice type is I slice, the set of QPdifference values is determined so that the factor (predeterminedvalue)=3, when the slice type is P slice, the set of QP differencevalues is determined so that the factor=2, and when the slice type is Bslice, the set of QP difference values is determined so that the factor(predetermined value)=1. Hereinafter, the respective methods in Examples1 to 3 are identified by method=0, 1, 2.

The following explains a specific example of how to generate a QPdifference value table when the set of QP difference values isdetermined according to the Examples 1 to 3.

In a case where the set of QP difference values is determined accordingto the Example 1, a QP difference value table to be included in a sliceheader of a P slice is one shown in (b) of FIG. 8 for example.

That is, the QP difference value table which the side informationdetermination section 21 incorporates into the slice header is a tablein which indices mb_qp_delta_index[j]=(−1)^(j+1)*Ceil (j/2) are relatedto individual QP difference values mb_qp_delta[j]=2*(−1)^(j+1)*Ceil(j/2) (j=0−8). In the case of the Example 1, the relation between the QPdifference value and the index is QP difference value=factor* index.

In the case where the set of QP difference values is determinedaccording to the Example 2, the QP difference value table to beincorporated into the slice header of the P slice is one shown in (c) ofFIG. 8 for example.

That is, the QP difference value table which the side informationdetermination section 21 incorporates into the slice header is a tablein which an index 0 is related to a QP difference value 0 and indicesmb_qp_delta_index[j]=(−1)^(j+1)*Ceil (j/2) are related to individual QPdifference values mb_qp_delta[j]=(−1)^(j+1)*2^({Ceil(j/2)−1})(j=1-8).

In the case where the set of QP difference values is determinedaccording to the Example 3, the QP difference value table which the sideinformation determination section 21 incorporates into the slice headeris a table in which indices 0, 1, and −1 are related to QP differencevalues 0, 1, and −1, and indices mb_qp_delta_index[j]=(−1)^(j+1)*Ceil(j/2)+3 (j=3, . . . ) are related to individual QP difference valuesmb_qp_delta[j]=(−1)^(j+1)*factor^({Ceil(j/2)−1}) (j=3, . . . ).

As described above, it is desirable that the side informationdetermination section 21 generates a QP difference value table in whichindividual QP difference values are related to indices whose absolutevalues are smaller than absolute values of the QP difference values(table shown in (a) to (c) of FIG. 8). The QP difference value tablegenerated by the side information determination section 21 should haveat least the characteristics below.

That is, the QP difference value table may be any table as long as theamount of codes of all quantization data outputted when individualindices are transformed into code numbers and subjected to aquantization process based on unary binarization is smaller than theamount of codes of all quantization data outputted when individual QPdifference values are transformed into code numbers and are subjected toa quantization process based on unary binarization. For example, the QPdifference value table may be a table in which QP difference values andindices are related to each other one by one, and the total of absolutevalues of individual indices is smaller than the total of absolutevalues of individual QP difference values.

(Operations of Side Information Determination Section 21 and SideInformation Encoding Section 22)

Next, an explanation is made as to operations of side informationdetermination section 21 and side information encoding section 22 withreference to FIG. 2. That is, an explanation is made as to operations ofindividual sections from the time when the video encoding device 2generates a QP difference value table with respect to each slice (asshown in (a) of FIG. 7) included in the input image #100 to the timewhen the video encoding device 2 encodes indices stored in a macroblocklayer of each macroblock MBi in the slice.

FIG. 2 is a flow chart showing the flow of the above operations.

As shown in FIG. 2, the side information determination section 21generates a QP difference value table corresponding to the slice type ofa slice included in the input image #100, and incorporates the QPdifference value table into a corresponding slice header in the sideinformation #21 (step S41).

Next, the side information determination section 21 determines the QPvalue of the macroblock MBi (i=1, 2, . . . ) in the slice (step S42).

Specifically, the side information determination section 21 temporarilysets the QP value of the macroblock MBi to be within the range definedby the H264/AVC standard. Then, the side information determinationsection 21 judges whether the value (temporal QP difference value)obtained by subtracting the already determined QP value of themacroblock MBi−1 from the temporarily set QP value of the macroblock MBiis included as a QP difference value in the QP difference value table.

In a case where the side information determination section 21 judgesthat the temporal QP difference value is included in the QP differencetable, the side information determination section 21 determines thetemporarily set QP value as the QP value of the macroblock MBi. On theother hand, in a case where the side information determination section21 judges that the temporal QP difference value is not included in theQP difference table, the side information determination section 21determines, as the QP value of the macroblock MBi, a value obtained byadding one of a plurality of QP difference values included in the QPdifference value table which one is closest to the temporal QPdifference value to the QP value of the macroblock MBi−1 (when i=1,slice default QP value).

As described above, after determining the QP values of individualmacroblocks, the side information determination section 21 subtracts theslice default QP value from the QP value of the headmost macroblock MB1to obtain the QP difference value for the headmost macroblock MB1. Then,the side information determination section 21 refers to the QPdifference value table generated in the immediately preceding step S41and transforms the QP difference value to an index (step S43). The sideinformation determination section 21 incorporates the obtained indexinto a corresponding macroblock layer in the side information #21.

Here, the QP difference value is transformed into the index by using theQP difference value table. In a case where a relation between the QPdifference value and the index is defined by calculations such as fouroperations, transform is possible without using the QP difference valuetable. Hereinafter, a rule for setting transform of a QP differencevalue to an index by calculation or transform of an index to a QPdifference value by calculation is referred to as a transform rule. Forexample, in the case of the Example 1, the transform rule is QPdifference value=index×factor, and accordingly transform of a QPdifference value into an index is possible by calculation without usingthe QP difference value table.

Furthermore, with respect to another macroblock MBi (i>1) for which QPdifference value is not yet calculated, the side informationdetermination section 21 calculates the QP difference value for themacroblock MBi by subtracting the QP value of the macroblock MBi−1 fromthe QP value of the macroblock MBi. Then, the side informationdetermination section 21 transforms the QP difference value into anindex by referring to the QP difference value table generated in theimmediately preceding step S41 (step S44). The side informationdetermination section 21 incorporates the obtained index into acorresponding macroblock layer in the side information #21.

After the step S44, the side information determination section 21determines whether the macroblock treated in the step S44 is the lastmacroblock MBn in the slice (step S45). When the side informationdetermination section 21 determines that the macroblock treated in thestep S44 is not the last macroblock MBn in the slice, the process goesback to the step S44. On the other hand, when the side informationdetermination section 21 determines that the macroblock treated in thestep S44 is the last macroblock MBn in the slice, the process goes tothe step S46.

The side information determination section 21 judges whether a slicewhich has not been subjected to treatments in the steps S41 to S44exists in the input image #100 or not (step S46). When the sideinformation determination section 21 judges that such a slice exists,the side information determination section 21 subjects the slice whichhas not been subjected to the treatments in the steps S41 to S44 to thetreatments in the steps S41 to S44. On the other hand, when the sideinformation determination section 21 judges that such a slice does notexist, the side information determination section 21 supplies, to theside information encoding section 22 and the MB setting section 23, theside information #21 whose macroblock layer includes indices and whoseslice header includes a QP difference value table. Then, the processgoes to the step S47.

With respect to the indices in individual macroblock layers in the sideinformation #21, the side information encoding section 22 to which theside information #21 has been inputted transforms the indices into codenumbers and carries out a binarization process on the input code numbersbased on unary binarization. That is, an index whose absolute value is nis transformed into a binary sequence with a length of 2n or 2n+1 (i.e.binary sequence with a length corresponding to the size of the absolutevalue of the index) based on the table shown in (a) of FIG. 9 (stepS47).

Furthermore, the side information encoding section 22 transforms binarysequences having been stored in individual macroblock layers in theprocess of the step S47 into algebraic signs, and encodes the QPdifference value tables included in individual slice headers in the sideinformation #21 (step S48). The side information encoding section 22carries out an encoding process on the whole of the side information #21(including the process of S48) and then supplies the encoded sideinformation #22 to the variable-length code multiplexing section 25.

An explanation was made above as to the operations of the sideinformation determination section 21 and the side information encodingsection 22. Here, an explanation is made as to the operation of the MBsetting section 23 to which the side information #21 is inputted.

As described above, the MB setting section 23 divides the input image#100 into a plurality of slices, and divides each slice into a pluralityof macroblocks. Then, the MB setting section 23 sequentially suppliesthe macroblock images #23 regarding individual macroblocks together withQP values regarding the macroblock images #23 to the MB encoding section24.

The MB setting section 23 calculates, based on the input sideinformation #21, the QP value to be supplied to the MB encoding section24 as follows.

That is, the MB setting section 23 refers to: an index included in amacroblock layer corresponding to the macroblock image #23; and a QPdifference value table included in a slice header corresponding to aslice partially constituted by the macroblock image #23.

Then, the MB setting section 23 refers to a QP difference value relatedto the referred index in the QP difference value table. Furthermore, theMB setting section 23 regards, as a QP value to be supplied to the MBencoding section 24, a value obtained by adding the QP difference valueto the QP value for the macroblock image #23 which value was supplied tothe MB encoding section 24 immediately before.

The MB encoding section 24 for quantizing and encoding the macroblockimage #23 based on an input QP value and members ranging from thevariable-length code multiplexing section 25 to the frame memory 27operate in accordance with the H264/AVC standard, and accordinglydetails thereof are omitted here.

(Encoding of QP Difference Value Table)

The following specifically explains encoding of a QP difference value bythe side information encoding section 22.

The side information encoding section 22 encodes the size of the QPdifference value table (i.e. the number of indices (QP differencevalues) in the table) and individual QP difference values.

For example, in a case where the side information determination section21 generates the QP difference value table as shown in (b) of FIG. 8,the side information encoding section 22 encodes the size 9 of the QPdifference value table and individual QP difference values (−8, −6, . .. , 0, . . . , 6, 8). Alternatively, instead of encoding individual QPdifference values, the side information encoding section 22 may encode aQP difference value corresponding to the index 0 as it is and as forother index, encode a difference obtained by subtracting, from saidother index, a QP difference value of index smaller by 1 than said otherindex.

QP difference values or differences of the QP difference values may beencoded by unary binarization.

With reference to (a) and (b) of FIG. 10, an amount of codes when the QPdifference value table shown in (b) of FIG. 8 is encoded based on unarybinarization is described below for two cases: a case where individualQP difference values are encoded as they are, and a case where a QPdifference value corresponding to the index 0 is encoded as it is and asfor other index, a difference of a QP difference value corresponding toother index is encoded. mb_qp_delta[i] in (a) and (b) of FIG. 10indicates a QP difference value of an index i. In (b) of FIG. 10,dd[i,i−1]=mb_qp_delta[i]-mb_qp_delta[i−1].

In the case where individual QP difference values are encoded as theyare, a QP difference value mb_qp_delta[−4] (=−8) is transformed into acode number 16, so that the amount of codes of the QP difference valueis 17 (see (a) of FIG. 10). Encoding of other QP difference values ismade in the same manner, so that the total of the amount of codes ofindividual QP difference values is 85 bits.

In the case where a QP difference value corresponding to the index 0 isencoded as it is and as for other index, a difference of a QP differencevalue corresponding to other index is encoded, the QP difference value(mb_qp_delta[0]=0) is transformed into a code number 0 so that theamount of codes is 1. Furthermore, as for other index i, the differencedd[i, i−1]=2 of a QP difference value is transformed into a code number3, so that the amount of codes is 4. Therefore, the total amount ofcodes is 29 bits.

Modification Example

The following explains a modification example of the operations of theside information determination section 21 and the side informationencoding section 22 with reference to FIG. 3 and (b) of FIG. 7. FIG. 3is a flow chart showing the operations of the side informationdetermination section 21 and the side information encoding section 22 ofthe present Modification Example. (b) of FIG. 7 is a view showing aslice constituted by a plurality of enlarged macroblocks (second unitregion) each constituted by a plurality of macroblocks. Here, eachenlarged macroblock is configured such that all macroblocks therein havesimilar pixel characteristics.

In the present Modification Example, the video encoding device 2determines the QP difference value with respect to each of a pluralityof macroblocks included in an enlarged macroblock. A macroblock forwhich the QP difference value is determined is selected in raster scanorder in each enlarged macroblock. For example, QP difference values forfour macroblocks in an enlarged macroblock LMB1 are determined in theorder of MB1, MB2, MB3, and MB4.

The video encoding device 2 carries out the above process with respectto each of the plurality of enlarged macroblocks in the slice. Theenlarged macroblock to be subjected to the above process is selected inraster scan order in the slice. For example, a plurality of enlargedmacroblocks in a slice in (b) of FIG. 7 are subjected to the aboveprocess in the order of enlarged macroblocks LMB1, LMB2, LMB3, . . . .As is seen from (b) of FIG. 7 and the above explanation, the number i inthe sign MBi (i=1, 2, . . . ) assigned to the macroblock in the drawingindicates the order by which the macroblock is selected in the slice.

In the present Modification Example, the video encoding device 2 assignsa QP value to a headmost macroblock (specific unit region) in anenlarged macroblock by a method based on the H264/AVC standard(hereinafter, the QP value of the headmost macroblock is also referredto as QP_(head)). The video encoding device 2 transforms the QPdifference value directly into a code number without transforming the QPvalue into an index, and transforms the code number into a binarysequence by unary binarization.

On the other hand, with respect to macroblocks other than the headmostmacroblock in one enlarged macroblock, the video encoding device 2transforms the QP difference value for the QP value assigned to theheadmost macroblock in that enlarged macroblock into an index based onthe QP difference value table shown in (e) of FIG. 8. Then, the videoencoding device 2 transforms the index into a code number and transformsthe code number into a binary sequence by unary binarization.

As is seen from (e) of FIG. 8, in the present Modification Example, thenumber of QP values assignable to macroblocks other than the headmostmacroblock (three QP values of QP_(head)−2, QP_(head), QP_(head)+2) issmaller than the number of QP values assignable to individualmacroblocks in the above Embodiment (thirteen in the case of using thetable shown in (a) of FIG. 8 and nine in the case of using the tablesshown in (b) to (d) of FIG. 8. Furthermore, in the present ModificationExample, the maximum value of the absolute value of the QP differencevalue that can be determined for a macroblock other than the headmostmacroblock is 2 which is a predetermined number close to 0.

It is deemed that since individual macroblocks in the enlargedmacroblock have similar image characteristics, assigning substantially aconstant QP value to individual macroblocks as above hardly causesdeterioration in quality of macroblock images, increase in the amount ofunnecessary codes etc. due to assignment of improper QP values.Furthermore, downsizing of the QP difference value table results in amerit that the amount of codes for encoding the QP difference valuetable can be reduced, too, and the absolute value of the index being 1at most results in a merit that the amount of codes of a binary sequenceinto which the index has been transformed is 2 or less.

The following explains the operations of the side informationdetermination section 21 and the side information encoding section 22 ofthe Modification Example with reference to FIG. 3.

As shown in FIG. 3, the side information determination section 21generates a QP difference value table as shown in (e) of FIG. 8, andincorporates the QP difference value table into a corresponding sliceheader in the side information #21 (step S61).

Individual macroblocks selected in raster scan order from a plurality ofmacroblocks constituting the whole of a target enlarged macroblock (e.g.LMB1) are subjected to the processes of S62 to S68 below in the order ofselection (e.g. the order of MB1, MB2, MB3, and MB4). Furthermore, thetarget macroblocks are selected in raster scan order (the order of LMB1,LMB2 . . . ) from a plurality of enlarged macroblocks constituting thewhole of a slice.

In the step S62, the side information determination section 21 judgeswhether the selected macroblock MBi is a headmost macroblock MB1 in aslice.

When the side information determination section 21 judges that theselected macroblock MBi is the headmost macroblock MB1 (YES in stepS62), the side information determination section 21 determines the QPvalue of the macroblock MB1 by a method based on the H264/AVC standard.Then, the side information determination section 21 causes the QPdifference value obtained by subtracting a slice default QP value fromthe determined QP value to be stored in a corresponding macroblock layer(step S67), and the process goes to the step S68.

On the other hand, when the side information determination section 21judges that the selected macroblock MBi is not the headmost macroblockMB1 (NO in step S62), the side information determination section 21judges whether the selected macroblock MBi is a headmost macroblock inone of other enlarged macroblocks (MB5, MB9 etc.) (step S63).

When the side information determination section 21 judges that theselected macroblock MBi is a headmost macroblock in an enlargedmacroblock (YES in step S63), the side information determination section21 determines the QP value of the macroblock MBi by a method based onthe H264/AVC standard. Then, the side information determination section21 causes the QP difference value obtained by subtracting the QP valuedetermined for the macroblock MBi−1 from the determined QP value for themacroblock MBi to be stored in a corresponding macroblock layer (stepS66), and the process goes to the step S68.

On the other hand, when the side information determination section 21judges that the selected macroblock MBi is not a headmost macroblock inan enlarged macroblock (NO in step S63), the side informationdetermination section 21 determines the QP difference value of themacroblock (step S64).

Specifically, the side information determination section 21 temporarilysets the QP value of the macroblock based on the H264/AVC standard.Then, the side information determination section 21 subtracts, from thetemporarily set QP value, a QP value of a headmost macroblock includedin the same enlarged macroblock as the macroblock is included in toobtain a temporal QP difference value, and judges whether the temporalQP difference value is included as a QP difference value in the QPdifference value table.

When the side information determination section 21 determines that thetemporal QP difference value is included as a QP difference value in theQP difference value table, the side information determination section 21determines the temporarily set QP value as the QP value of themacroblock MBi. On the other hand, when the side informationdetermination section 21 determines that the temporal QP differencevalue is not included as a QP difference value in the QP differencevalue table, the side information determination section 21 determines,as the QP difference value of the macroblock MBi, a QP difference valueclosest to the temporal QP difference value out of the plurality of QPdifference values included in the QP difference value table. That is,the number of candidates of QP difference values to be determined formacroblocks other than the headmost macroblock in the enlargedmacroblock in the step S64 is smaller than the number of candidates ofQP difference values to be determined for the headmost macroblock in theenlarged macroblock. A value obtained by adding the determined QPdifference value to the QP value of the macroblock MBi−1 is determinedas the QP value of the macroblock MBi.

The side information determination section 21 refers to the QPdifference value table generated in the immediately preceding step S61,and transforms the QP difference value determined in the step S64 intoan index. The side information determination section 21 incorporates theobtained index into a corresponding macroblock layer in the sideinformation #21 (step S65), and the process goes to the step S68.

In the step S68, the side information determination section 21 judgeswhether the macroblock having been processed is the last macroblock inthe slice. When the side information determination section 21 determinesthat the macroblock having been processed is not the last macroblock (NOin the step S68), the process goes to the step S62. On the other hand,when the side information determination section 21 determines that themacroblock having been processed is the last macroblock (YES in the stepS68), the process goes to the step S69.

The side information determination section 21 judges whether a slicehaving not been subjected to the processes in the steps S61 to S68exists in the input image #100 or not (step S69). When judging that sucha slice exists, the side information determination section 21 subjectsthe slice to the process in the steps S61 to S68. On the other hand,when judging that such a slice does not exist, the side informationdetermination section 21 supplies the side information #21 to the sideinformation encoding section 22 and the MB setting section 23 and theprocess goes to the step S70.

The side information encoding section 22 receives the side information#21, and transforms indices or QP difference values included inindividual macroblock layers in the side information #21 into codenumbers, and subjects the code numbers to a binarization process basedon unary binarization (step S70).

Furthermore, the side information encoding section 22 encodes QPdifference value tables included in individual slice headers in the sideinformation #21 (step S71). The side information encoding section 22carries out an encoding process (including the process in S70) on thewhole of the side information #21 and then supplies the encoded sideinformation #22 to the variable-length code multiplexing section 25.

An explanation was made above as to the operations of the sideinformation determination section 21 and the side information encodingsection 22. Here, an explanation is made as to the operation of the MBsetting section 23 to which the side information #21 is inputted.

On the basis of the input side information #21, the MB setting section23 calculates a QP value to be supplied together with the macroblockimage #23 to the MB encoding section 24.

That is, when the macroblock image #23 to be supplied is a macroblockother than a headmost macroblock in an enlarged macroblock, the MBsetting section 23 refers to an index included in the macroblock layercorresponding to the macroblock image #23 and a QP difference valuetable included in a slice header corresponding to a slice partiallyconstituted by the macroblock image #23. Then, the MB setting section 23refers to the QP difference value related to the index which the MBsetting section has referred to in the QP difference value table.Furthermore, the MB setting section 23 adds the QP difference value tothe QP value regarding the macroblock image #23 supplied to the MBencoding section 24 just before, thereby obtaining a QP value to besupplied to the MB encoding section 24.

On the other hand, when the macroblock image #23 to be supplied is aheadmost macroblock in an enlarged macroblock, the MB setting section 23refers to a QP difference value included in a macroblock layercorresponding to the macroblock image #23. The MB setting section 23adds the QP difference value to the QP value regarding the macroblockimage #23 supplied to the MB encoding section 24 just before, therebyobtaining a QP value to be supplied to the MB encoding section 24.

<Additional Matters Regarding Video Encoding Device>

It was described above that it is desirable that the side informationdetermination section 21 generates a QP difference value table in whichindividual QP difference values are related to indices whose absolutevalues are smaller than absolute values of the QP difference values asshown in (a) to (c) of FIG. 8. Alternatively, the side informationdetermination section 21 may generate a table of (d) of FIG. 8 which isnot designed as above. The table of (d) of FIG. 8 is generated as below.

That is, as described above, in the step S42, the side informationdetermination section 21 determines, with respect to each of themacroblocks MB1 to MBn in the slice, the QP difference value for themacroblock out of the set of the QP difference values determined for theslice so as to determine the QP value of the macroblock.

The side information determination section 21 generates a table in whichthe most frequent value (0 in (d) of FIG. 8), the second frequent value(4 in (d) of FIG. 8), the third frequent value (−6 in (d) of FIG. 8) . .. which are set based on the n determined QP difference values arerelated to indices 0, 1, −1, . . . . That is, in the table, a morefrequent QP difference value is related to an index with a smallerabsolute value. Furthermore, individual frequencies, i.e. ratios ofindividual QP difference values included in a group consisting of n QPdifference values are calculated by the side information determinationsection 21. In a case where QP difference value table is generated insuch a manner that QP difference values with higher frequencies aregiven indices will smaller absolute values, the total sum of theabsolute values of the QP difference values included in the QPdifference value table may be equal to the total sum of the absolutevalues of the indices.

An explanation was made above as to the video encoding device 2 inaccordance with the present Embodiment. However, the present inventionis not limited to the above configuration.

(Additional Matter 1)

In the above Embodiment, the quantization unit region is a macroblock.However, the present invention is not limited to this. That is, althoughan explanation was made above as to a case where determination of a QPvalue, transform of a QP difference value into an index, binarization ofan index, and quantization of an image by using the QP value are madewith respect to each macroblock, such operations may be made not withrespect to each macroblock but with respect to a unit larger than themacroblock or a unit smaller than the macroblock (i.e. with respect toeach partition, each block of 8 pixels×8 lines, each block of 4 pixels×4lines etc.).

In the above Embodiment, the table generation unit region is a slice.However, the present invention is not limited to this. That is, althoughan explanation was made as to a case where the QP difference value tableis generated with respect to each slice, the QP difference value tablemay be generated with respect to a unit larger than the slice (withrespect to each picture etc.) or a unit smaller than the slice (withrespect to each macroblock etc.). In a case of generating the QPdifference value table corresponding to the values of factor in eachmacroblock, for example, the macroblock type of a macroblock layer isreferred to, and when the macroblock type is an intramacroblock, it maybe determined that factor=3, and when the macroblock type is anintermacroblock, it may be determined that factor=2.

However, it should be noted that regardless of how the size of a tablegeneration unit region and the size of a quantization unit region aredetermined, the table generation unit region must include a plurality ofquantization unit regions.

Alternatively, the present invention may be arranged such that the QPdifference value table is not generated with respect to each tablegeneration unit region. That is, a predetermined QP difference valuetable is stored in a storage section (not shown), and the QP differencevalue table stored in the storage section is used instead of a QPdifference value table generated with respect to each table generationunit region. In this case, it is unnecessary for the video encodingdevice 2 to encode the QP difference value table and output the encodedQP difference value table to the outside. This is because when the videodecoding device 1 has the same QP difference value table, the videodecoding device 1 can derive the QP difference value from the indexafter decoding side information encoded data #11 a.

(Additional Matter 2)

In the above Embodiment, the slice type is determined with respect toeach slice, the value of factor is determined according to the slicetype, and the QP difference value table according to the value of factoris generated. Alternatively, the QP difference value table may begenerated as follows.

That is, initially, the side information determination section 21temporarily sets QP values of macroblocks MB1 to MBn included in a sliceby a method based on the H264/AVC standard. Then, the side informationdetermination section 21 calculates dispersion of the obtained n QPvalues, and determines the value of factor according to the size ofdispersion. Specifically, for example, when dispersion is not less thanS₁, it is determined that factor=3. When dispersion is not less than S₂and less than S₁, it is determined that factor=2. When dispersion isless than S₂, it is determined that factor=1. Lastly, the sideinformation determination section 21 generates a QP difference valuetable corresponding to the value of factor thus determined.

(Additional Matter 3)

In the above Embodiment, when the QP difference value table is encoded,individual QP difference values are encoded. Alternatively, the QPdifference value table may be encoded as follows. That is, as shown bythe QP difference value table of (b) of FIG. 8 and the QP differencevalue table of (c) of FIG. 8, when the QP difference value tabledetermined by the value of factor and the size of the QP differencevalue table is encoded, the value of factor may be encoded instead ofencoding individual QP difference values. In this case, the amount ofcodes of the QP difference value table is further reduced. As shown bythe Examples 1 to 3, there are a plurality of methods for calculatingthe QP difference value table from the same factor. The presentinvention may be arranged to select and use one of the methods shown bythe Examples 1 to 3. In this case, information necessary for determiningthe method for calculating the QP difference value table may beexplicitly encoded. That is, both of method and factor may be encoded.

Information to be outputted as encoded data to the outside may be anyinformation as long as the information relates individual QP differencevalues to indices one by one. The information may be encoded QPdifference values or may be encoded values of factor. In a case wherethe range of an index registered in a QP difference value table isvariable with respect to each slice, the information may include notonly individual QP difference values or the values of factor but alsothe values of indices.

The video encoding device and the video decoding device may be arrangedto each include a plurality of predetermined transform rules or aplurality of QP difference value tables and encodes a transform ruleindex (roughness-specifying flag) for switching the plurality oftransform rules (or the plurality of QP difference value tables). In acase of encoding the transform rule index, there may be encoded a 0-2transform rule index designed such that, for example, an index foridentifying a transform rule mb_qp_delta=mb_qp_delta_index is 0, anindex for identifying a transform rule indicated by the QP differencevalue table shown in (b) of FIG. 8 is 1, and an index for identifying atransform rule equivalent to a QP difference value table shown in (c) ofFIG. 8.

The roughness-specifying flag for identifying the QP difference valuetable may be a binary flag. For example, a value of theroughness-specifying flag for identifying a QP difference value tableequivalent to a transform rule mb_qp_delta=mb_qp_delta_index is set to0, and a value of a roughness-specifying flag for identifying the QPdifference value table shown in (a) of FIG. 8 is set to 1.

(Additional Matter 4)

In the above Embodiment, unary binarization is used in order totransform an index into a binary sequence. However, the presentinvention is not limited to this. Alternatively, in order to transforman index into a binary sequence, unary binarization or fixed-lengthbinarization as shown in (b) of FIG. 9 may be used depending on thesituation. Furthermore, a binary sequence obtained by thesebinarizations may be subjected to another encoding. For example,Context-based Adaptive Binary Arithmetic Coding (CABAC) defined in H.264/AVC may be applied.

Specifically, the side information encoding section 22 may determinewhether to use unary binarization or fixed-length binarization withrespect to each slice. In this case, with respect to each macroblock ina slice, the side information encoding section 22 refers to an indexstored in a corresponding macroblock layer. Then, the side informationencoding section 22 may judge whether a ratio of a plurality of indiceswhich the side information encoding section 22 has referred to includingthe value of an index i (i=0, 1, . . . ) is substantially constant(whether the difference between the maximum value and the minimum valueof the ratio is not more than a predetermined threshold), and when theratio is substantially constant, the side information encoding section22 may use fixed-length binarization and when otherwise, the sideinformation encoding section 22 may use unary binarization.

The length of a binary sequence obtained by fixed-length binarizationdepends on logarithm of the number of possible QP difference values witha radix of 2. For example, when the number of possible QP differencevalues is 7, the length of a binary sequence is 3. Therefore, in a casewhere the possible QP difference values are limited by using a QPdifference value table, the length of the binary sequence is reducedcompared with a case of not limiting QP difference values and so theamount of codes is reduced, too.

(Additional Matter 5)

In the present invention, a QP difference value of a quantization unitregion of interest is obtained from a difference between a QP value ofthe quantization unit region of interest and a predetermined referencevalue. In the above Embodiment, the predetermined reference value is aQP value of a quantization unit region just before the quantization unitregion of interest in the order of processing. However, the presentinvention is not limited to this. That is, the predetermined referencevalue may be a QP value of a quantization unit region adjacent to thequantization unit region the QP difference value of which is to beobtained (e.g. quantization unit region-adjacent to the quantizationunit region of interest to the left or to the above). Alternatively, thepredetermined reference value may be a QP value of a quantization unitregion close to the quantization unit region the QP difference value ofwhich is to be obtained (i.e. quantization unit region positioned in apredetermined range from the quantization unit region of interest), ormay be a value that changes with respect to each process unit largerthan a quantization unit (e.g. slice default QP value). Alternatively,the predetermined reference value may be a specific constant (e.g. 0).

(Advantages of Video Encoding Device 2)

As described above, the video encoding device 2 sets the QP value ofeach macroblock in such a manner that the QP difference value of a pairof macroblocks with consecutive orders of encoding is one of n QPdifference values. For example, the video encoding device 2 sets the QPvalue of the macroblock MB3 in such a manner that the QP differencevalue of the macroblock MB3 with respect to the macroblock MB2 is 1which is one of nine QP difference values registered in the QPdifference value table shown in (d) of FIG. 8: −9, −2, . . . , 3, and 8.Then, the video encoding device 2 transforms the QP difference value 1of the macroblock MB3 with respect to the macroblock MB2 into an index 2corresponding to the QP difference value 1 out of 9 indices.

Furthermore, the side information encoding section 22 generates a binarysequence having a length corresponding to the size of the absolute valueof the index. For example, the side information encoding section 22generates a binary sequence “1110” having a length of 4 from the indexof 2, and generates a binary sequence “111110” having a length of 6 fromthe index 3.

The total of absolute values of n indices is smaller than the total ofabsolute values of n difference values. For example, in the QPdifference value table shown in (d) of FIG. 8, the total of absolutevalues of 9 indices is 20, whereas the total of absolute values of 9 QPdifference values is 34. Accordingly, transforming QP difference valuesof the macroblocks MB1 to MBn into corresponding indices and generatingbinary sequences having lengths corresponding to the sizes of absolutevalues of the indices provides, in general, a smaller total length of nbinary sequences (i.e. smaller amount of codes) than conventionallygenerating, from QP difference values of the macroblocks MB1 to MBn,binary sequences having lengths corresponding to the sizes of absolutevalues of the QP difference values.

Consequently, the video encoding device 2 can reduce the amount of codesof quantization parameters compared with a conventional art.

(Video Decoding Device)

The following explains a configuration of the video decoding device(decoding device) 1 in accordance with the Embodiment with reference toFIGS. 4-10 and 12. The video decoding device 1 is a video decodingdevice a part of which uses the technique employed in the H264/AVCstandard.

Schematically, the video decoding device 1 is a device which decodesencoded data #1 from the video encoding device 2 so as to generate andoutput a decoded image #2.

FIG. 4 is a block diagram showing a configuration of the video decodingdevice 1. As shown in FIG. 4, the video decoding device 1 includes avariable-length code inverse-multiplexing section 11, a side informationdecoding section 12, a MB setting section 13, a MB decoding section 14,and a frame memory 15.

The encoded data #1 inputted to the video decoding device 1 is inputtedto the variable-length code inverse-multiplexing section 11. Thevariable-length code inverse-multiplexing section 11 reverse-multiplexesthe input encoded data #1 so as to divide the encoded data #1 into sideinformation encoded data #11 a which is encoded data regarding sideinformation and encoded data #11 b which is encoded data regarding apicture, and outputs the side information encoded data #11 a and theencoded data #11 b to the side information decoding section 12 and theMB setting section 13, respectively.

The side information decoding section 12 decodes side information #12from the side information encoded data #11 a, and outputs the sideinformation #12 to the MB setting section 13. The side information #12includes a picture parameter set which is the set of parametersregarding the input image #100, a slice header which is headerinformation with respect to each slice included in the input image #100,a macroblock layer which is the set of parameters with respect to eachmacroblock included in the slice, and the like.

The MB setting section 13 divides, based on the input side information#12, the encoded data #11 b into a plurality of slices and divides eachslice into individual encoded data #13 corresponding to individualmacroblocks, and sequentially outputs the individual encoded data #13 tothe MB decoding section 14. As mentioned later, the MB setting section13 calculates, based on the side information #12, a QP value forreverse-quantizing the encoded data #13, and outputs the obtained QPvalue together with the encoded data #13 to the MB decoding section 14.

The MB decoding section 14 sequentially decodes and reverse-quantizesthe encoded data #13 corresponding to individual inputted macroblocks(reverse-quantized unit region) so as to generate and output decodedimages #2 corresponding to individual macroblocks. Furthermore, thedecoded images #2 are outputted to the frame memory 15, too.

The decoded images #2 are stored in the frame memory 15. At the time ofdecoding a certain macroblock, in the frame memory 15, decoded imagescorresponding to all macroblocks preceding the certain macroblock in theorder of processing.

At the time when all the macroblocks constituting the encoded data #11 bhave been subjected to a decoded image generation process by the MBdecoding section 14 with respect to each macroblock, a process forgenerating the decoded images #2 corresponding to the encoded datainputted to the video decoding device 1 is completed.

(Regarding Operations of the Side Information Decoding Section 12 andthe MB Setting Section 13)

Next, an explanation is made as to the operations of the sideinformation decoding section 12 and the MB setting section 13 withreference to FIG. 5. FIG. 5 is a flowchart showing the flow of theoperations of the side information decoding section 12 and the MBsetting section 13.

As shown in FIG. 5, the side information decoding section 12 decodes aQP difference value table included in each slice header from the sideinformation encoded data #11 a (step S1). Thereafter, the sideinformation decoding section 12 takes out, from the side informationencoded data #11 a, an index included in each macroblock layer (stepS2). Specifically, the side information decoding section 12 generates abinary sequence by arithmetic-decoding data having beenarithmetic-encoded in the step S48 by the side information encodingsection 22 of the video encoding device 2, and subjects the binarysequence to a reverse process of unary binarization (conversion ofbinary sequence into multivalued sequence) so as to take out an index.Then, the side information decoding section 12 supplies side information#12 including the QP difference value table and the index to the MBsetting section 13.

Then, the MB setting section 13 calculates QP values to be sequentiallyoutputted together with the encoded data #13 to the MB decoding section14 (step S3).

Specifically, the MB setting section 13 refers to the QP differencevalue table included in a slice header of the side information #12 andto the index included in a macroblock layer (macroblock layercorresponding to macroblock indicated by the encoded data #13) of theside information #12. Here, the slice header of the side information #12is a slice header corresponding to a slice partially constituted by amacroblock indicated by the encoded data #13. Then, the MB settingsection 13 refers to a QP difference value related to the index in theQP difference value table, and calculates a QP value from the QPdifference value.

The MB decoding section 14 for decoding the input encoded data #13 andreverse-quantizing the decoded data based on a QP value inputtedtogether with the encoded data #13, and the frame memory 15 operate inaccordance with the H264/AVC standard, and therefore details thereof areomitted here.

Modification Example

The following explains a modification example of the operations of theside information decoding section 12 and the MB setting section 13 withreference to FIG. 6 and (b) of FIG. 7. FIG. 6 is a flowchart showing theoperations of the side information decoding section 12 and the MBsetting section 13.

The side decoding section 12 and the MB setting section 13 operate inaccordance with the present Modification Example when the sideinformation determination section 21 and the side information encodingsection 22 of the video encoding device 2 operate in accordance with thepresent Modification Example.

As shown in FIG. 6, the side information decoding section 12 decodes aQP difference value table included in each slice header from the sideinformation encoded data #11 a (step S21).

All macroblock layers included in the side information encoded data #11a are subjected to the processes of S22 and subsequent steps mentionedbelow. The macroblock layers subjected to the processes of S22 andsubsequent steps are selected in the same order as the order forselecting macroblocks to be processed by the side informationdetermination section 21 of the video encoding device 2. In a case ofthe slice shown in (b) of FIG. 7, the macroblock layer corresponding tothe macroblock MBi is subjected to S22 and subsequent steps at the i-thorder.

The side information decoding section 12 judges whether the selectedmacroblock layer is a macroblock layer of the headmost macroblock(specific unit region) in an enlarged macroblock (second unit region)(step S22).

When the side information decoding section 12 judges that the selectedmacroblock layer is not a macroblock layer of the headmost macroblock(NO in step S22), the side information decoding section 12 takes out anindex included in the macroblock layer from the side information encodeddata #11 a (step S23). Specifically, the side information decodingsection 12 subjects the binary sequence generated in the step S70 by theside information encoding section 22 of the video encoding device 2 to areverse process of unary binarization (conversion of binary sequenceinto multivalued sequence) so as to take out an index. Then, the sideinformation decoding section 12 supplies the side information #12including the QP difference value table and the index to the MB settingsection 13.

Furthermore, the MB setting section 13 calculates a QP value to beoutputted together with the encoded data #13 to the MB decoding section14 (step S24).

Specifically, the MB setting section 13 refers to the QP differencevalue table included in the slice header of the side information #12 andthe index included in the macroblock layer. Then, the MB setting section13 refers to a QP difference value related to the index in the QPdifference value table, and calculates a QP value from the QP differencevalue by a method based on the H264/AVC standard.

On the other hand, when the side information decoding section 12 judgesthat the selected macroblock layer is a macroblock layer of the headmostmacroblock (YES in step S22), the side information decoding section 12takes out a QP difference value included in the macroblock layer fromthe side information encoded data #11 a, and the MB setting section 13calculates a QP value (step S25). Specifically, the side informationdecoding section 12 takes out a QP difference value corresponding to amultivalued integer obtained by subjecting the binary sequence generatedin the step S70 by the side information encoding section 22 of the videoencoding device 2 to a reverse process of unary binarization (conversionof binary sequence into multivalued sequence). Then, the sideinformation decoding section 12 supplies the side information #12including the QP difference value to the MB setting section 13, and theMB setting section 13 calculates a QP value from the QP difference valueincluded in the side information #12 by a method based on the H264/AVCstandard.

When all the macroblock layers have been subjected to the processes ofthe steps S23 and S24 (or the process of the step S25) (YES in stepS26), the process is finished. When there is a macroblock layer havingnot been subjected to the process (NO in step S26), the process goes tothe step S22.

<Additional Matters Regarding Video Decoding Device>

An explanation was made above as to the video decoding device 1 inaccordance with the present Embodiment. However, the present inventionis not limited to the above.

(Additional Matter 1)

In the above Embodiment, the inverse-quantization unit region is amacroblock. However, the present invention is not limited to this. Thereverse phase quantization unit region may be a unit region larger thana macroblock or smaller than a macroblock as long as the size of aninverse-quantization unit region is the same as the size of aquantization unit region in the video encoding device 2.

In the above Embodiment, the QP value for inverse-quantization of animage of each inverse-quantization unit region is calculated from the QPdifference value. In this case, the QP difference value table in theslice header is referred to in order to obtain the QP difference valuefrom the index. That is, the QP difference value tables to be referredto in order to obtain the QP difference value from the index areswitched with respect to each slice. However, the decoding device of thepresent invention is not limited to this. The QP difference value tablesto be referred to may be switched with respect to each unit region ofthe same size as the table generation unit region of the video encodingdevice 2.

(Additional Matter 2)

A specific process for decoding the QP difference value table may be asfollows.

In a case where encoded data of the QP difference value table includesencoded data of individual QP difference values included in the QPdifference value table, each QP difference value may be decoded by areverse process of unary binarization.

Furthermore, in a case where the encoded data of the QP difference valuetable includes the value of factor and the size of the QP differencevalue table, these are decoded. In this case, the QP difference valuetable may be generated based on the decoded value of factor and thedecoded size of the QP difference value table. That is, in a case wherethe size of the QP difference value table is 2n+1 and the value offactor is f, there may be generated a QP difference value table in whichindices are set to be −n, −n+1, . . . , 0, . . . , n−1, and n, and theQP difference values corresponding to the indices, respectively, are setto −1*f*n, −1*f*(n−1), . . . , 0, f*(n−1), and f*n.

(Advantage of Video Decoding Device 1)

As described above, the video decoding device 1 carries out a processfor setting quantization parameters regarding individual macroblocksconstituting a decoded image. The side information decoding section 12extracts binary sequence data regarding individual macroblocks from theencoded data #1. Then, the side information decoding section 12generates indices corresponding to the length of binary sequences fromthe binary sequence data.

Then, the MB setting section 13 refers to the QP difference value tablein which mutually different n indices are related to n QP differencevalues one by one, thereby specifying the QP difference values ofindividual macroblocks from the indices which the side informationdecoding section 12 has generated with respect to each of themacroblocks. Thereafter, the MB setting section 13 calculates QP valuesof individual macroblocks from the QP difference values by a methodbased on the H264/AVC standard.

Therefore, the video decoding device 1 subjects individual macroblocksto the inverse-quantization process using the calculated QP values,thereby generating a decoded image constituted by the macroblocks.

Second Embodiment (Encoded Data)

Initially, with reference to FIG. 13, an explanation is made as toencoded data which is generated by a video encoding device in accordancewith each of Second Embodiment and subsequent embodiments and which isreferred to by a video decoding device in accordance with each of SecondEmbodiment and subsequent embodiments. In the explanation below, a sign“4” of a video encoding device, a sign “3” of a video decoding device,and a sign “#4” of encoded data indicate the video encoding device inaccordance with Second Embodiment, the video decoding device inaccordance with Second Embodiment, and encoded data referred to inSecond Embodiment, respectively. Encoded data referred to by videoencoding devices and video decoding devices in accordance with ThirdEmbodiment and subsequent embodiments can be understood by replacing thesigns used in the following explanation with signs used in thoseembodiments.

(Configuration of Encoded Data)

With reference to FIG. 13, an explanation is made below as to aconfiguration example of encoded data #4 which is generated by the videoencoding device 4 and which is decoded by the video decoding device 3.The encoded data #4 includes, for example, a sequence and a plurality ofpictures constituting the sequence.

FIG. 13 shows structures of a picture layer and subsequent layers in theencoded data #4. (a) to (d) of FIG. 13 show a picture layer defining apicture PICT, a slice layer defining a slice S, a tree block layerdefining a tree block TBLK, and a CU layer defining a coding unit (CU)included in the tree block TBLK.

(Picture Layer)

In the picture layer, a set of data to be referred to by the videodecoding device 3 in order to decode a picture PICT which is to beprocessed (which may be hereinafter referred to as target picture) isdefined. As shown in (a) of FIG. 13, the picture PICT includes a pictureheader PH and slices S₁ to S_(NS) (NS indicates the total number ofslices included in the picture PICT).

In the explanation below, when it is unnecessary to distinguish theslices S₁ to S_(NS) from each other, the individual codes may bedescribed while omitting subscripts of the codes. The same is applied toother data which is included in the encoded data #4 explained below andto which a subscript is added.

The picture header PH includes encoding parameters to be referred to bythe video decoding device 3 in order to determine a method for decodinga target picture. For example, encoding mode information(entropy_coding_mode_flag) indicative of the mode of variable-lengthencoding which is used when the video encoding device 4 encodes is anexample of an encoding parameter included in the picture header PH.

In a case where entropy_coding_mode_flag is 0, the picture PICT isencoded by CAVLC (Context-based Adaptive Variable Length Coding). In acase where entropy_coding_mode_flag is 1, the picture PICT is encoded byCABAC (Context-based Adaptive Binary Arithmetic Coding).

The picture header PH is also referred to as a picture parameter set(PPS).

FIG. 16 is a view showing syntax included in the picture parameter set.As shown in FIG. 16, the picture parameter set includes syntaxlog2_min_delta_qualt_coding_unit_size_minus4. The video decoding devicein accordance with the present embodiment generatesMinDeltaQuantCodingUnitSize as size information by referring to thesyntax.

A Descriptor u(1) shown in FIG. 16 indicates that syntax related tothese descriptors is subjected to fixed codeword length coding by 1 bit,u(2) indicates that syntax related to this descriptor is subjected tofixed codeword length coding by 2 bit, and ue(v) indicates that syntaxrelated to this descriptor is subjected to variable codeword lengthcoding (the same is applicable to a syntax table below).

(Slice Layer)

In the slice layer, a set of data to be referred to by the videodecoding device 3 in order to decode a slice S to be processed (whichmay be also referred to as target slice) is defined. As shown in (b) ofFIG. 13, the slice S includes a slice header SH and tree blocks TBLK₁ toTBLK_(NC) (NC indicates the total number of tree blocks included in theslice 5).

The slice header SH includes encoding parameters to be referred to bythe video decoding device 1 in order to determine a method for decodinga target slice. Slice type designating information (slice_type) fordesignating a slice type is an example of an encoding parameter includedin the slice header SH.

Examples of the slice type that can be designated by the slice typedesignating information include (1) I slice which uses onlyintra-prediction in encoding, (2) P slice which uses single-directionprediction or intra-prediction in encoding, and (3) B slice which usessingle-direction prediction, two-direction prediction, orintra-prediction.

Further, the slice header SH may include a filter parameter to bereferred to by a loop filter (not shown) included in the video decodingdevice 1.

(Tree Block Layer)

In the tree block layer, a set of data to be referred to by the videodecoding device 3 in order to decode a tree block TBLK to be processed(which may be also referred to as a target tree block) is defined.

The tree block TBLK includes a tree block header TBLKH and coding unitinformation CU₁ to CU_(NL) (NL indicates the total number of coding unitinformation included in the tree block TBLK). Initially, an explanationis made below as to a relation between the tree block TBLK and thecoding unit information CU.

The tree block TBLK is divided into partitions for specifying the sizeof a block for intra-prediction or inter-prediction and transformprocesses.

The partitions of the tree block TBLK are obtained by recursive quadtreedivision. A tree structure obtained by this recursive quadtree divisionis hereinafter referred to as a coding tree.

Hereinafter, a partition corresponding to a leaf which is a node at anend of the coding tree is referred to as a coding node. Since the codingnode is a basic unit in a coding process, the coding node is hereinafteralso referred to as a coding unit (CU).

That is, coding unit information (hereinafter referred to as CUinformation) CU₁ to CU_(NL) is information corresponding to coding nodes(coding units) obtained by subjecting the tree block TBLK to recursivequadtree division.

Furthermore, a root of the coding tree is made to correspond to the treeblock TBLK. In other words, the tree block TBLK is made to correspond toa top node of a quadtree structure recursively including a plurality ofcoding nodes.

The size of each encoding node is a half both in vertical and horizontaldirections of the size of an encoding node to which that coding nodedirectly belong (i.e. partition of a node which is superior by one layerto that encoding node).

The possible size of individual coding nodes depends on size designatinginformation for a coding node and maximum hierarchical depth which areincluded in a sequence parameter set SPS of the encoded data #4. Forexample, in a case where the size of the tree block TBLK is 64×64 pixelsand the maximum hierarchical depth is 3, the size of a coding node at alayer of the tree block TBLK or below that layer can be one of threekinds of sizes: 64×64 pixels, 32×32 pixels, and 16×16 pixels.

(Tree Block Header)

A tree block header TBLKH includes a coding parameter to be referred toby the video decoding device 3 in order to determine a method fordecoding a target tree block. Specifically, as shown in (c) of FIG. 13,the tree block header TBLKH includes tree block dividing informationSP_TBLK for designating a division pattern for individual CUs of thetarget tree block and a quantization parameter difference Δqp (qp_delta)for designating the size of a quantization step.

The tree block dividing information SP_TBLK is information indicative ofa coding tree for dividing tree blocks. Specifically, the tree blockdividing information SP_TBLK is information for designating the shapeand the size of individual CUs included in the target tree block and theposition of individual CUs in the target tree block.

The tree block dividing information SP_TBLK is not required toexplicitly include the shape and the size of a CU. For example, the treeblock dividing information SP_TBLK may be a set of flags indicative ofwhether a target tree block as a whole or a partial region of the treeblock is to be subjected to quadtree division or not(split_coding_unit_flag). In this case, the shape and the size of eachCU can be specified by using the shape and the size of the tree block.

Furthermore, the quantization parameter difference Δqp is a differenceqp−qp′ between a quantization parameter qp in the target tree block anda quantization parameter qp′ in a tree block which has been encoded justbefore the target tree block.

(CU Layer)

In the CU layer, a set of data to be referred to by the video decodingdevice 3 in order to decode a CU to be processed (which is hereinafteralso referred to as a target CU) is defined.

Here, prior to specifically explaining data included in the CUinformation CU, an explanation is made as to a tree structure of dataincluded in CU. The coding node serves as a root node of a predictiontree (PT) and a transform tree (TT). The following explains theprediction tree and the transform tree.

In the prediction tree, a coding node is divided into one or a pluralityof prediction blocks, and the positions and the sizes of individualprediction blocks are defined. In other words, the prediction block isone or a plurality of non-overlapping regions constituting the codingnode. Furthermore, the prediction tree includes one or a plurality ofprediction blocks obtained by the above division.

A prediction process is carried out with respect to each predictionblock. Hereinafter, the prediction block serving as a unit of predictionis also referred to as a prediction unit (PU).

In general, there are two kinds for division in the prediction tree. Oneis intra-prediction and the other is inter-prediction.

In the case of intra-prediction, the division may be made based on 2N×2N(the same size as that of the coding node) or N×N.

In the case of inter-prediction, the division may be made based on 2N×2N(the same size as that of the coding node), 2N×N, N×2N, N×N or etc.

Furthermore, in the transform tree, a coding node is divided into one ora plurality of transform blocks, and the positions and the sizes ofindividual transform blocks are defined. In other words, the transformblock is one or a plurality of non-overlapping regions constituting thecoding node. Furthermore, the transform tree includes one or a pluralityof transform blocks obtained by the above division.

Division in the transform tree includes assigning a region with a sizeequal to that of the coding node as a transform block, and recursivequadtree division like the division in the tree block.

A transform process is carried out with respect to the transform block.Hereinafter, the transform block serving as a unit of transform is alsoreferred to as a transform unit (TU).

(Data Structure of CU Information)

Subsequently, an explanation is made as to specific contents of dataincluded in CU information with reference to (d) of FIG. 13. As shown in(d) of FIG. 13, the CU information includes a skip flag SKIP, PTinformation PTI, and TT information TTI.

The skip flag SKIP is a flag for showing whether a skip mode is appliedto a target PU or not. In a case where the skip flag SKIP is 1, i.e. theskip mode is applied to a target CU, the PT information PTI and the TTinformation TTI in the CU information are omitted. The skip flag SKIP isomitted in the I slice.

The PT information PTI is information regarding PT in CU. In otherwords, the PT information PTI is a set of information regarding one or aplurality of PUs included in PT and is referred to by the video decodingdevice 3 when generating a prediction image. As shown in (d) of FIG. 13,the PT information PTI includes prediction type information PType andprediction information PInfo.

The prediction type information PType is information for designating useof intra-prediction or use of inter-prediction as a method forgenerating a prediction image for a target PU.

The prediction information PInfo is constituted by intra-predictioninformation or inter-prediction information according to whichprediction method the prediction type information PType designates.Hereinafter, PU to which intra-prediction is applied is also referred toas intra PU, and PU to which inter-prediction is applied is alsoreferred to as inter PU.

Furthermore, the prediction information PInfo includes information fordesignating the shape, the size, and the position of a target PU. Asdescribed above, the prediction image is generated with respect to eachPU as a unit. The prediction information PInfo is detailed later.

The TT information TTI is information regarding TT included in CU. Inother words, the TT information TTI is a set of information regardingone or a plurality of TUs included in TT, and is referred to by thevideo decoding device 1 when decoding residual error data. Hereinafter,TU is also referred to as a block.

As shown in (d) of FIG. 13, the TT information TTI includes TT divisioninformation SP_TT for designating a division pattern for individualtransform blocks in a target CU, and quantization prediction residualerrors QD₁ to QD_(NT) (NT indicates the total number of blocks includedin the target CU).

Specifically, the TT division information SP_TT is information fordetermining the shape and the size of individual TUs included in thetarget CU and the position of individual TUs in the target CU. Forexample, the TT division information SP_TT can be realized by includinginformation indicative of whether to divide a target node or not(split_transform_unit_flag) and information indicative of the depth ofthe division (trafoDepth).

Furthermore, in a case where the size of CU is 64×64, the size ofindividual TUs obtained by division can range from 32×32 pixels to 2×2pixels.

The quantization prediction residual error QD is coding data generatedby the video encoding device 4 carrying out processes 1 to 3 below on atarget block to be processed.

Process 1: prediction residual error obtained by subtracting aprediction image from an encoding target image is subjected to DCT(Discrete Cosine Transform);

Process 2: transform coefficient obtained in the process 1 is quantized;

Process 3: transform coefficient quantized in the process 2 is subjectedto variable codeword length coding.

The aforementioned quantization parameter qp indicates the size of aquantization step QP used by the video encoding device 2 when quantizinga transform coefficient (QP=2^(qp/6)).

(Prediction Information PInfo)

As described above, there are two kinds of the prediction informationPInfo: the inter-prediction information and the intra-predictioninformation.

The inter-prediction information includes a coding parameter to bereferred to by the video decoding device 3 when generating aninter-prediction image by inter-prediction. To be specific, theinter-prediction information includes inter PU division information fordesignating a division pattern for individual inter PUs of a target CUand inter-prediction parameters for individual inter PUs.

The inter-prediction parameter includes a reference image index, anestimated motion vector index, and motion vector residual error.

On the other hand, the intra-prediction information includes a codingparameter to be referred to by the video decoding device 3 whengenerating an intra-prediction image by intra-prediction. To be morespecific, the intra-prediction information includes intra-PU divisioninformation for designating a division pattern for individual intra-PUsof a target CU and intra-prediction parameters for individual intra-PUs.The intra-prediction parameter is a parameter for designating anintra-prediction method (prediction mode) for individual intra-PUs.

Hereinafter, in Second Embodiment and subsequent embodiments, “TU”indicates a transform block at the bottom node of a transform tree.Furthermore, “LCU” indicates a CU at the top node of a coding tree.

(Video Decoding Device)

The video decoding device in accordance with the present embodiment is adevice for decoding the encoded data #4 from the video encoding device 4(which will be explained below) to generate the decoded image #3.

The following details the video decoding device in accordance with thepresent embodiment with reference to drawings.

Initially, an explanation is made as to a configuration of the videodecoding device in accordance with the present embodiment with referenceto FIG. 14. FIG. 14 is a block diagram showing the configuration of thevideo decoding device 3. As shown in FIG. 14, the video decoding device3 includes a variable-length code inverse-multiplexing section 31, aside information decoding section 32, a CU setting section 33, a CUdecoding section 34, and a frame memory 15.

The encoded data #4 inputted to the video decoding device 3 is inputtedto the variable-length code inverse-multiplexing section 31. Thevariable-length code inverse-multiplexing section 31 reverse-multiplexesthe input encoded data #4 so as to divide the encoded data #4 into sideinformation encoded data #31 a which is encoded data regarding sideinformation and encoded data #31 b which is encoded data regarding apicture, and outputs the side information encoded data #31 a and theencoded data #31 b to the side information decoding section 32 and theCU setting section 33, respectively.

The side information decoding section 32 decodes the side informationencoded data #31 a to generate side information #32, and outputs theside information #32 to the CU setting section 33.

When decoding the side information encoded data #31 a, the sideinformation decoding section 32 decodes encoded data of size informationindicative of the size of a QP encoded unit region, thereby generatingthe size information as a part of the side information #32.Specifically, the side information decoding section 32 subjectslog2_min_delta_qualt_coding_unit_size_minus4 included in the sideinformation encoded data #31 a to calculation by equation 1 below,thereby generating MinDeltaQuantCodingUnitSize as the size information.In the equation 1, “<<” indicates left bit shift calculation.

[Mathematical Formula 1]

MinDeltaQuantCodingUnitSize=1<<(log2_min_delta_qualt_coding_unit_size_minus4+4)  Formula1

Furthermore, when decoding the side information encoded data #31 a, theside information decoding section 32 decodes encoded data of a QPdifference value of each QP encoding unit region, thereby generating theQP difference value as a part of the side information #32.

More specifically, the side information decoding section 32 sequentiallycarries out a process below on individual CUs by referring to acoding_unit syntax (see FIG. 18) included in the encoded data #4. Thatis, when x-component and y-component of the upper left coordinates of aCU for which a skip flag (skip_flag) is to be referred to are equal tointeger multiples of the size of a QP encoding unit region(MinDeltaQuantCodingUnitSize), the side information decoding section 32sets a value of a flag indicative of whether decodable or not(deltaQuantAvail) to “true” indicative of a decodable state. Then, theside information decoding section 32 decodes the QP difference value ata time of decoding a CU other than the skip block while deltaQuantAvailindicates a decodable state. That is, when referring to a skip flag “0”while deltaQuantAvail is “true”, the side information decoding section32 decodes cu_qp_delta included in the coding_unit syntax, and sets theQP difference value of a CU for which the skip flag has been referred tothe value of decoded cu_qp_delta. Subsequently, the side informationdecoding section 32 sets the value of deltaQuantAvail to “false”.

In a case where the value of deltaQuantAvail is “false”, the sideinformation decoding section 32 refers to a skip flag whose value is“0”, and sets 0 to the QP difference value. The value of qp at CUdecoded immediately before the CU for which the skip flag was referredto is used as qp for the CU for which the skip flag was referred to.

Alternatively, in consideration of a merge block which is a CU for whichthe same prediction parameter as that for an adjacent block, cu_qp_deltamay be decoded as follows. With respect to each of one or more CUsconstituting the whole of each QP encoding unit region, the sideinformation decoding section 32 may refer to a skip flag of the CU and amerge flag of the CU in raster scan order. In this case, with respect toeach QP encoding unit region, the side information decoding section 32decodes, from cu_qp_delta, a QP difference value of a CU for which skipflag “0” and merge flag “0” are referred to firstly in the QP encodingunit region.

Specifically, the side information decoding section 32 may sequentiallycarry out a process below on individual CUs by referring to acoding_unit syntax (see FIG. 19) included in the encoded data #4. Thatis, when x-component and y-component of the upper left coordinates of aCU for which a skip flag (skip_flag) is to be referred to are equal tointeger multiples of the size of a QP encoding unit region(MinDeltaQuantCodingUnitSize), the side information decoding section 32sets a value of a flag indicative of whether decodable or not(deltaQuantAvail) to “true” indicative of a decodable state. Then, theside information decoding section 32 decodes cu_qp_delta at a time ofdecoding a CU which is neither a skip block nor a merge block. That is,when referring to both a skip flag “0” and a merge flag “0” whiledeltaQuantAvail is “true”, the side information decoding section 32decodes cu_qp_delta included in the coding_unit syntax, and sets the QPdifference value of a CU for which the skip flag has been referred tothe value of decoded cu_qp_delta. Subsequently, the side informationdecoding section 32 sets the value of deltaQuantAvail to “false”.

The side information decoding section 32 does not encode a QP differencevalue at the time of decoding a CU of a skip block or a merge blockwhile deltaQuantAvail indicates “false”. That is, when referring to askip flag “1” while deltaQuantAvail indicates “false”, or when referringto both a skip flag “0” and a merge flag “1” while deltaQuantAvailindicates “false”, the side information decoding section 32 sets the QPdifference value to 0. In this case, the value qp of a CU decodedimmediately before the CU for which the skip flag is referred to is usedas qp for the CU for which the skip flag is referred to.

As described above, as a result of the process by the side informationdecoding section 32, qp is set uniquely for each QP encoding unitregion. qp set uniquely for each QP encoding unit region is used incommon among CUs included in the QP encoding unit region.

In accordance with the input side information #32, the CU settingsection 33 divides the encoded data #31 b into a plurality of slices,divides each slice into a plurality of QP encoding unit regions,separates each QP encoding unit region into encoded data #33 bcorresponding to individual CUs, and outputs the encoded data #33 bsequentially to the CU decoding section 34. Furthermore, the CU settingsection 33 outputs, to the CU decoding section 34, a QP difference value#33 a of each QP encoding unit region included in the side information#32 as well as the encoded data #33 b corresponding to individual CUs inthe QP encoding unit region.

The CU decoding section 34 sequentially decodes and reverse-quantizesthe encoded data #33 b corresponding to inputted individual CUs(reverse-quantized unit region) to generate decoded images #34corresponding to individual CUs and outputs the decoded images #34. Thedecoded images #34 are outputted to the frame memory 15, too.

Specifically, when decoding and reverse-quantizing the encoded data #33b corresponding to a CU, the CU decoding section 34 obtains a QP valuefrom the QP difference value #33 a of the QP encoding unit region towhich the CU belongs, and carries out an inverse-quantization process.

At a time when the decoded image generation process by the CU decodingsection 34 with respect to each CU is completed for all CUs constitutingthe encoded data #31 b, a process of generating the decoded image #3corresponding to encoded data inputted to the video decoding device 3 iscompleted.

As described above, the video decoding device decodes encoded data of aQP difference value not with respect to each CU but with respect to eachQP encoding unit region consisting of one or more CUs, and accordinglycan generate a decoded image from encoded data with the smaller amountof codes than a conventional art.

Furthermore, a skip block which is a CU without residual error data doesnot require qp. In consideration of this, when the skip flag is “1”, theQP difference value is not decoded, and only when the skip flag is “0”,the QP difference value is decoded. This allows reducing the amount ofcodes of the QP difference value in encoded data.

Similarly with a skip block, also in a marge block in which a part ofencoded data is omitted in order to reduce the amount of codes of theencoded data, a QP difference value is not decoded, thereby allowingreduction of the amount of codes of the QP difference value in theencoded data.

(Video Coding Device)

A video encoding device in accordance with the present embodimentcarries out a process of dividing each LCU constituting the input imageinto a plurality of CUs (Coding Unit: quantization unit region) by usinga coding_tree syntax described in JCTVT-403. As is seen from thecoding_tree syntax, the dividing process is specifically a recursiveprocess of dividing a CU at an i th node into four CUs at an i+1 th nodewith a one-fourth size when split_coding_unit_flag of a CU at the i-thnode is true. Therefore, the sizes of the plurality of CUs are notidentical with each other in general.

Furthermore, the video encoding device is designed to encode, withrespect to each QP encoding unit region (unit region) consisting of oneor more CUs, a QP difference value regarding one CU at most belonging tothe QP encoding unit region. Furthermore, the video encoding device isdesigned to encode size information indicative of the size of the QPencoding unit region.

That is, the video encoding device in accordance with the presentembodiment does not encode a QP difference value with respect to eachquantization unit region like the video encoding device in accordancewith First Embodiment, but encodes a QP difference value with respect toeach QP encoding unit region consisting of one or more quantization unitregions, thereby reducing the amount of codes of the QP differencevalue.

The thus encoded QP difference value of each QP encoding unit region andthe thus encoded size information of each QP encoding unit region aretransmitted to a later-mentioned video decoding device. Then, the videodecoding device carries out inverse-quantization using a QP differencevalue common among quantization unit regions constituting one QPencoding unit region.

A region (third unit region) constituting the QP encoding unit regionmay be TU instead of CU.

The following details the video encoding device in accordance with thepresent embodiment with reference to drawings.

Initially, an explanation is made as to a configuration of a videoencoding device 4 in accordance with the present embodiment withreference to FIG. 15. FIG. 15 is a block diagram showing a configurationof the video encoding device 4. As shown in FIG. 15, the video encodingdevice 4 includes a side information determination section 41, a sideinformation encoding section 42, a CU setting section 43, a CU encodingsection 44, a variable-length code multiplexing section 25, a CUdecoding section 46, and a frame memory 27.

The side information determination section 41 determines sideinformation in accordance with an input image #100, and outputs thedetermined side information as side information #41. The sideinformation #41 (and later-mentioned side information #61, #81 etc. aswell) includes a picture parameter set #7 which is a set of parametersregarding the input image #100, a slice header which is headerinformation with respect to each slice included in the input image #100,CU information which is a set of parameters with respect to each CUincluded in a slice, TU information which is a set of parameters withrespect to each TU included in a CU etc.

Specifically, the side information determination section 41 determinesthe (longitudinal and lateral) size of a QP encoding unit region inaccordance with a predetermined algorithm with respect to each slice (oreach picture), and causes size information indicative of the size of theQP encoding unit region to be stored in a slice header (pictureparameter set) of the side information #41.

Furthermore, the side information determination section 41 defines a QPencoding unit region constituting the input image #100 (or each slice)in accordance with size information for the QP encoding unit region inthe picture parameter set (or slice header), and causes a QP differencevalue regarding one CU at most per each QP encoding unit region(hereinafter also referred to merely as “QP difference value of a QPencoding unit region”) to be stored as a part of CU information of theCU in the side information #41.

The side information encoding section 42 encodes the side information#41 and outputs side information encoded data #42. The side informationencoded data #42 is supplied to the variable-length code multiplexingsection 25. When encoding the side information #41, the side informationencoding section 42 encodes a QP difference value of each QP encodingunit region and the size information.

Specifically, the side information encoding section 42 applieslogarithmic function having 2 as a base to the size of a QP encodingunit region to obtain a logarithmic function value and subtracts 4 fromthe logarithmic function value, thereby generating encoded data of sizeinformation. When a picture parameter set includes size information,encoded data of the picture parameter set is data shown in FIG. 16 forexample (in FIG. 16, log2_min_delta_qualt_coding_unit_size_minus4indicates encoded data of size information).

The CU setting section 43 divides the input image #100 into a pluralityof slices in accordance with the side information #41, and divides eachslice into a plurality of CUs, and outputs CU images #43 regardingindividual CUs. As mentioned above, individual CU images have differentsizes in general.

Furthermore, the CU setting section 43 outputs CU images #43 b regardinga plurality of CUs constituting one QP encoding unit region and a QPdifference value #43 a of the QP encoding unit region which is stored inthe side information #41.

The CU encoding section 44 carries out DCT transformation of predictiveresiduals between sequentially input CU images #43 b and a predictedimage transmitted from a predicted image generation section (not shown)and quantizes DCT coefficients of the predictive residuals atquantization levels corresponding to QP values determined according toQP difference values #43 a of QP encoding unit regions to which the CUimages #43 b belong. Then, the CU encoding section 44 subjects the dataobtained by quantization to a variable-length encoding process togenerate CU encoded data #44 and supplies the CU encoded data #44 to thevariable-length code multiplexing section 25.

The CU decoding section 46 sequentially decodes the CU encoded data #44corresponding to inputted CU images #43 b, respectively, therebygenerating and outputting decoded images #46 corresponding to CUs,respectively. The decoded images #46 are supplied to the frame memory27.

The variable-length code multiplexing section 25 and the frame memory 27have been already explained in First Embodiment and thereforeexplanations thereof are omitted here.

An explanation was made above as to the configuration of the videoencoding device 4. An explanation is made below, with reference to FIG.17, as to a specific process carried out by the side informationdetermination section 41 and the side information encoding section 42 inorder to encode one QP difference value at most with respect to each QPencoding unit region.

FIG. 17 is a view schematically showing a part of a QP encoding unitregion (four QP encoding unit regions) defined by the side informationdetermination section 41. Each of four square regions surrounded by athick line in FIG. 17 is a QP encoding unit region, and twelve regionssurrounded by a thin line is a CU. In FIG. 17, a CU with hatched linesis a CU whose QP difference value is to be encoded, and a CU with dotsis a skip block.

The side information determination section 41 refers to, in apredetermined order (in the raster scan order in the presentembodiment), a skip flag of each of at least one CU constituting thewhole of each QP encoding unit region defined by the side informationdetermination section 41. With respect to the QP encoding unit region,the side information determination section 41 calculates a QP value of aCU for which a skip flag “0” is referred to firstly in the QP encodingunit region, and outputs, as a part of the side information #41, a QPdifference value between the QP value of that CU and a QP value referredto immediately before the QP value of that CU (or default QP value) tothe side information encoding section 42.

For example, with respect to the encoding unit region at the upper rightside of FIG. 17, since the CU positioned initially in the raster scanorder is a skip block (CU whose skip flag value is “1”), the sideinformation determination section 41 calculates the QP value of a CUwith hatched lines positioned secondly in the raster scan order, andoutputs a QP difference value between the QP value of that CU and adefault QP value to the side information encoding section 42.

The side information encoding section 42 encodes, with respect to eachQP encoding unit region, a QP difference value of one CU at most in theQP encoding unit region. The QP difference value is stored in the sideinformation #41.

Specifically, the side information determination section 41 and the sideinformation encoding section 42 sequentially subject individual CUs to aprocess below by using a coding unit syntax shown in FIG. 18. That is,when x-component and y-component of the upper left coordinates of a CUwhose skip flag (skip_flag) is referred to are integer-multiples of thesize of the QP encoding unit region (MinDeltaQuantCodingUnitSize), theside information determination section 41 sets the value of a flagindicative of whether encoding is possible or not (deltaQuantAvail) to“true”. Then, when the side information determination section 41 refersto a skip flag “0” while the value of deltaQuantAvail is “true”, theside information determination section 41 supplies, as a part of theside information #41, the QP difference value of the CU whose skip flaghas been referred to, to the side information encoding section 42. Theside information encoding section 42 subjects the QP difference value toan encoding process and sets the value of deltaQuantAvail to “false”.

Alternatively, the side information determination section 41 may referto a skip flag and a merge flag of each of at least one CU constitutingthe whole of each QP encoding unit region defined by the sideinformation determination section 41. In this case, the side informationdetermination section 41 calculates a QP value of a CU for which a skipflag “0” and a merge flag “0” are referred to firstly in the QP encodingunit region, and outputs, as a part of the side information #41, a QPdifference value between the QP value of that CU and a QP value referredto immediately before the QP value of that CU (or default QP value) tothe side information encoding section 42.

Specifically, the side information determination section 41 and the sideinformation encoding section 42 may sequentially subject individual CUsto a process below by using a coding unit syntax shown in FIG. 19. Thatis, when x-component and y-component of the upper left coordinates of aCU whose skip flag (skip_flag) is referred to are integer-multiples ofthe size of the QP encoding unit region (MinDeltaQuantCodingUnitSize),the side information determination section 41 sets the value of a flagindicative of whether encoding is possible or not (deltaQuantAvail) to“true”. Then, when the side information determination section 41 refersto a skip flag “0” and a merge flag “0” at the same time while the valueof deltaQuantAvail is “true”, the side information determination section41 supplies, as a part of the side information #41, the QP differencevalue of the CU whose skip flag has been referred to, to the sideinformation encoding section 42. The side information encoding section42 subjects the QP difference value to an encoding process and sets thevalue of deltaQuantAvail to “false”.

As a result of the processes carried out by the side informationdetermination section 41 and the side information encoding section 42,the variable-length code multiplexing section 25 receives, from the sideinformation encoding section 42, side information encoded data #42including encoded data of QP difference values of individual QP encodingunit regions and size information of the QP encoding unit regionsdetermined with respect to each picture parameter set (each slice).Furthermore, the variable-length code multiplexing section 25multiplexes CU encoded data #44 received from the CU encoding section 44and the side information encoded data #42 to generate and output encodeddata #4.

The side information determination section 41 may cause size informationof the QP encoding unit region to be stored in a sequence parameter setinstead of a slice header and a picture parameter set.

(Additional Matter)

The side information encoding section 42 of the video encoding device 4applies logarithmic function having 2 as a base to the size of a QPencoding unit region to obtain a logarithmic function value andsubtracts 4 from the logarithmic function value. However, the presentinvention is not limited to this.

That is, the side information encoding section 42 may encode the size ofa QP encoding unit region relative to the size of an LCU. For example,in a case where the size of a QP encoding unit region is one-2^(n) ofthe size of an LCU (max_coding_unit_width), the side informationencoding section 42 may generate n as encoded data for size information.

In this case, the side information decoding section 32 of the videodecoding device 3 subjects log2_min_delta_qualt_coding_unit_size_to_lcuincluded in the side information encoded data #31 a to an operationbased on formula 2 below, and generates MinDeltaQuantCodingUnitSize asthe size information. In the formula 2, “>>” indicates right bit shiftoperation.

[Mathematical Formula 2]

MinDeltaQuantCodingUnitSize=max_coding_unit_width>>log2_min_delta_quant_unit_size_to_lcu  Formula2

The method for encoding the size of a QP encoding unit region as a sizerelative to the size of an LCU is applicable to embodiments below.

Third Embodiment (Encoded Data)

A configuration of encoded data #6 in accordance with the presentembodiment is substantially the same as the configuration of the encodeddata #4 explained in Second Embodiment except that the encoded data #6in accordance with the present embodiment includes a coding_unit syntaxshown in FIG. 20 and a transform_tree syntax shown in FIG. 21. Thecoding_unit syntax shown in FIG. 20 and the transform_tree syntax shownin FIG. 21 will be explained together with a video decoding device and avideo encoding device below.

(Video Decoding Device)

The video decoding device in accordance with the present embodiment hassubstantially the same configuration as that of the video decodingdevice 3 explained in Second Embodiment. The video decoding device inaccordance with the present embodiment operates in basicallysubstantially the same manner as the video decoding device 3 explainedin Second Embodiment, thereby decoding the encoded data #6 to generate adecoded image #3. However, a QP difference value of each QP encodingunit region is not a part of QP information of the side information #32,but a part of TU information of the side information #32. Accordingly, aCU setting section 33 of the video decoding device 3 refers to TUinformation of each selection target TU which is included in the sideinformation #32, thereby reading out a QP difference value of each QPencoding unit region.

The following explains this point more specifically.

A side information decoding section 32 included in the video decodingdevice in accordance with the present embodiment refers to, in theraster scan order, a skip flag and a residual data present flag(residualDataPresentFlag) of each of at least one CU constituting thewhole of each QP encoding unit region. Here, the residual data presentflag is a flag that becomes “true” when a CU includes at least one TUincluding at least one DCT coefficient which is not 0, and becomes“false” when otherwise.

By referring to a coding unit syntax shown in FIG. 20 and atransform_tree syntax shown in FIG. 21, the side information decodingsection 32 sequentially subjects individual CUs to a process below. Thatis, as is seen from FIG. 20, when x-component and y-component of theupper left coordinates of a CU whose skip flag (skip_flag) is referredto are integer-multiples of the longitudinal and lateral size of a QPencoding unit region (MinDeltaQuantCodingUnitSize), the side informationdecoding section 32 sets the value of a flag indicative of whetherdecoding is possible or not (deltaQuantAvail) to “true”. Then, when theside information decoding section 32 refers to a skip flag “0” while thevalue of deltaQuantAvail is “true”, the side information decodingsection 32 refers to the value of residualDataPresentFlag in thetransform_tree syntax shown in FIG. 21. When the value ofresidualDataPresentFlag is “0”, that is, when the TU does not includeresidual data, the side information decoding section 32 refers to thecoding unit syntax with respect to next CU. Whenentropy_coding_mode_flag is 0, residualDataPresentFlag is determineddepending on whether the value of cuv_yuv_root is 0 or not. Whencuv_yuv_root is other than 0, residualDataPresentFlag is “true”, andwhen cuv_yuv_root is 0, residualDataPresentFlag is “false”.

When entropy_coding_mode_flag is 0, residualDataPresentFlag is “true” ifno_resisulal_data_flag is other than 0, and residualDataPresentFlag is“false” if no_resisulal_data_flag is 0.

On the other hand, when the value of residualDataPresentFlag is “1”,that is, when the TU includes residual data, the side informationdecoding section 32 refers to the transform_tree syntax shown in FIG. 21with respect to each TU constituting a CU of interest. Consequently, theside information decoding section 32 decodes cu_qp_delta of a TU (e.g.TU at the lower right end. Hereinafter also referred to as “selectiontarget TU”) which includes at least one DCT coefficient other than 0 andwhich is firstly decoded in a predetermined order (e.g. order oppositeto raster scan order) out of TUs in the CU of interest, and sets the QPdifference value of the firstly decoded TU to the value of the decodedcu_qp_delta. Thereafter, the side information decoding section 32 setsthe value of deltaQuantAvail to “false”. The above process by the sideinformation decoding section 32 uniquely determines qp with respect toeach QP encoding unit region. qp uniquely determined with respect toeach QP encoding unit region is used commonly for CUs included in the QPencoding unit region.

(Video Encoding Device)

The following details the video encoding device in accordance with thepresent embodiment with reference to drawings.

Like the video encoding device 4 in accordance with Second Embodiment,the video encoding device in accordance with the present embodimentdivides each LCU constituting an input image into a plurality of CUs(Coding Unit: quantization unit region) by using a coding_tree syntax.Furthermore, unlike the video encoding device 4, the video encodingdevice in accordance with the present embodiment divides each CU into aplurality of transform units (TU) constituting a transform tree by usingthe coding_unit syntax shown in FIG. 20 and the transform_tree syntaxshown in FIG. 21.

Furthermore, the video encoding device is designed to encode only atleast a part of TUs constituting the whole of each QP encoding unitregion determined according to a predetermined algorithm constituted byone or more TUs mentioned above. It should be noted that the videoencoding device in accordance with the present embodiment encodes the QPdifference value of the TU only when predictive residual of the TU isother than 0 (i.e. when a DCT coefficient other than 0 is present).Absence of the DCT coefficient other than 0 is equal to DCT coefficientsof luminance components being 0 and DCT coefficients of color differencecomponents of the TU being 0. Accordingly, unlike Second Embodiment, thevideo encoding device in accordance with the present embodiment canreduce a redundant process of encoding a QP difference value which isnot necessary to encode.

The following explains the video encoding device 6 in accordance withthe present embodiment with reference to FIG. 22. FIG. 22 is a blockdiagram showing a configuration of the video encoding device 6. As shownin FIG. 22, the video encoding device 6 includes a side informationdetermination section 61, a side information encoding section 62, a CUsetting section 43, a CU encoding section 44, a variable-length codemultiplexing section 25, a CU decoding section 46, and a frame memory27.

The CU setting section 43, the CU encoding section 44, thevariable-length code multiplexing section 25, the CU decoding section46, and the frame memory 27 have been already explained in FirstEmbodiment or Second Embodiment. Accordingly, an explanation is madebelow as to the side information determination section 61 and the sideinformation encoding section 62.

With respect to each of one or more CUs constituting the whole of eachQP encoding unit region defined by the side information determinationsection 61, the side information determination section 61 refers to askip flag of the CU and a residual data present flag(residualDataPresentFlag) of the CU in the raster scan order. Here, theresidual data present flag is a flag which becomes “true” when a CUincludes at least one TU including at least one DCT coefficient otherthan 0 and which becomes “false” when otherwise. With respect to each QPencoding region, the side information determination section 61 outputs,as a part of side information #61, a QP difference value #63 a between aQP value of a CU whose skip flag “0” and residual data present flag “1”are referred to simultaneously for the first time in the QP encodingunit region and a default QP value, to the side information encodingsection 62.

With respect to each QP encoding unit region, the side informationencoding section 62 encodes the QP difference value received from theside information determination section 61 to generate encoded data #62.

Specifically, by using the coding unit syntax shown in FIG. 20 and thetransform_tree syntax shown in FIG. 21, the side informationdetermination section 61 and the side information encoding section 62sequentially subject individual CUs to a process below. That is, as isseen from FIG. 20, when x-component and y-component of the upper leftcoordinates of a CU whose skip flag (skip_flag) is referred to areinteger-multiples of the longitudinal and lateral size of a QP encodingunit region (MinDeltaQuantCodingUnitSize), the side informationdetermination section 61 sets the value of a flag indicative of whetherencoding is possible or not (deltaQuantAvail) to “true”. Then, when theside information determination section 61 refers to a skip flag “0”while the value of deltaQuantAvail is “true”, the side informationdetermination section 61 brings up the transform_tree syntax shown inFIG. 21 and refers to the value of residualDataPresentFlag. When thevalue of residualDataPresentFlag is “0”, the side informationdetermination section 61 brings up the coding unit syntax with respectto the next CU.

On the other hand, when the value of residualDataPresentFlag is “1”, theside information determination section 61 applies the transform treesyntax shown in FIG. 21 to each TU constituting the CU of interest.Consequently, the side information determination section 61 calculates aQP difference value of a TU (e.g. TU at the lower right end. Hereinafteralso referred to as “selection target TU”) which includes at least oneDCT coefficient other than 0 and which is firstly referred to in apredetermined order (e.g. order opposite to raster scan order) out ofTUs in the CU of interest, and supplies the QP difference value of theselection target TU as a part of TU information to the side informationencoding section 62. The side information encoding section 62 subjectsthe received QP difference value to an encoding process and sets thevalue of deltaQuantAvail to “false”.

As a result of the processes carried out by the side informationdetermination section 61 and the side information encoding section 62,the variable-length code multiplexing section 25 receives, from the sideinformation encoding section 62, side information encoded data #62including encoded data of QP difference values of individual QP encodingunit regions and size information of the QP encoding unit regionsdetermined with respect to each picture (or each slice constituting thepicture). Furthermore, the variable-length code multiplexing section 25multiplexes CU encoded data #44 received from the CU encoding section 44and the side information encoded data #62 to generate and output encodeddata #6.

(Additional Matter)

The side information determination section 61 and the side informationencoding section 62 may use a transform_tree syntax shown in FIG. 23instead of the transform_tree syntax shown in FIG. 21.

That is, the side information determination section 61 supplies not onlythe QP difference value of the selection target TU but also the QPdifference value of the TU which includes at least one DCT coefficientother than 0 and which is at the upper left end in the CU of interest asa part of TU information to the side information encoding section 62.

Furthermore, the side information determination section 61 and the sideinformation encoding section 62 may use a transform_tree syntax shown inFIG. 24 instead of the transform_tree syntax shown in FIG. 21.

That is, when the value of residualDataPresentFlag of the CU of interestis “1”, the side information determination section 61 may supply, as apart of CU information of the CU (i.e. TU at the uppermost node), the QPdifference value of the CU to the side information encoding section 62.

Fourth Embodiment (Video Decoding Device)

A video decoding device in accordance with the present embodiment is adevice for decoding encoded data #8 supplied from a video encodingdevice 8 to generate decoded images #7. An example of a coding unitsyntax included in encoded data #7 is shown in FIG. 27.

The following details the video decoding device in accordance with thepresent embodiment with reference to drawings.

Initially, with reference to FIG. 25, an explanation is made as to aconfiguration of the video decoding device in accordance with thepresent embodiment. FIG. 27 is a block diagram showing the configurationof a video decoding device 7. As shown in FIG. 25, the video decodingdevice 7 includes a variable-length code inverse-multiplexing section71, a side information decoding section 72, a CU setting section 73, aCU decoding section 74, a predicted image generation section 75, and aframe memory 15.

The encoded data #8 inputted to the video decoding device 7 is inputtedto the variable-length code inverse-multiplexing section 71. Thevariable-length code inverse-multiplexing section 71 reverse-multiplexesthe inputted encoded data #8 so as to divide the encoded data #7 intoside information encoded data #71 a which is encoded data regarding sideinformation and encoded data #71 b which is encoded data regarding apicture, and outputs the side information encoded data #71 a and theencoded data #71 b to the side information decoding section 72 and theCU setting section 73, respectively.

The side information decoding section 72 decodes the side informationencoded data #71 a to generate side information #72 and outputs the sideinformation #72 to the CU setting section 73.

In the process for decoding the side information encoded data #71 a, theside information decoding section 72 decodes encoded data of aprediction mode #88 m of each CU, thereby generating the prediction mode#88 m of each CU which serves as a part of side information #72.

In the process for decoding the side information encoded data #71 a, theside information decoding section 72 decodes encoded data of sizeinformation of a first QP encoding unit region (unit region) and asecond QP encoding unit region (fourth unit region) which data isincluded in the side information encoded data #71 a, thereby generatingthe two pieces of size information as a part of the side information#72. Specifically, the side information decoding section 72 subjectslog2 min_delta_qualt_coding_unit_size_minus4 to an operation based onthe formula 1 above, thereby generating MinDeltaQuantCodingUnitSize assize information of the first QP encoding unit region.

Furthermore, the side information decoding section 72 subjectslog2_min_intra_delta_qualt_coding_unit_size_minus4 included in the sideinformation encoded data #71 a to the same operation, thereby generatingMinIntraDeltaQuantCodingUnitSize as size information of the second QPencoding unit region.

The following specifically explains a process by the side informationdecoding section 72 for decoding a QP difference value 73 a.

The side information decoding section 72 refers to the coding unitsyntax shown in FIG. 27 and sequentially subjects individual CUs to aprocess below. That is, as is seen from FIG. 27, when x-component andy-component of the upper left coordinates of a CU whose skip flag(skip_flag) is referred to are equal to integer-multiples of the size ofthe first QP encoding unit region (MinDeltaQuantCodingUnitSize), theside information decoding section 72 sets the value of deltaQuantAail to“true”.

The side information decoding section 72 refers to the values ofindividual skip flags, and when referring to a skip flag “0”, the sideinformation decoding section 72 sets a flag indicative of whether a QPdifference value is decodable or not when a CU image is intra-coded(deltaQuantAvailIntra) to “true”. Furthermore, when referring to theskip flag “0” of a CU while the value of deltaQuantAvail is “true”, theside information decoding section 72 decodes cu_qp_delta included in thecoding_unit syntax, and sets the value of decoded cu_qp_delta as the QPdifference value of the CU whose skip flag has been referred to. Then,the side information decoding section 72 sets the values ofdeltaQuantAvail and deltaQuantAvailIntra to “false”.

Furthermore, also when x-component and y-component of the upper leftcoordinates of a CU whose skip flag (skip_flag) is referred to are equalto integer-multiples of the size of the second QP encoding unit region(MinIntraDeltaQuantCodingUnitSize) and the value of deltaQuantAvailIntrais “true”, the side information decoding section 72 decodes cu_qp_deltaincluded in the coding_unit syntax, and sets the value of decodedcu_qp_delta as the QP difference value of the CU whose skip flag hasbeen referred to.

In accordance with the input side information #72, the CU settingsection 73 divides the encoded data #71 b into a plurality of slices anddivides each slice into encoded data #73 b corresponding to individualCUs, and sequentially outputs the encoded data #73 b to the CU decodingsection 74. Furthermore, the CU setting section 73 outputs, in additionto the encoded data #73 b, prediction modes #73 m of individual CUs andQP difference values 73 a of individual selection target CUs that areincluded in the side information #72 to the CU decoding section 74.Furthermore, the CU setting section 73 outputs the prediction modes #73m of individual CUs to the predicted image generation section 75.

The CU decoding section 74 sequentially decodes and reverse-quantizesthe encoded data #73 b corresponding to inputted CUs(inverse-quantization unit region), respectively, thereby generating andoutputting decoded images #74 corresponding to the CUs, respectively.The decoded images #74 are also outputted to the frame memory 15.

Specifically, the CU decoding section 74 refers to the sizes of thefirst QP encoding unit region and the second QP encoding unit regionthat are stored in the inputted side information #72, and definesindividual QP encoding unit regions constituting the whole region of adecoded image to be generated.

Then, the CU decoding section 74 determines QP difference values used ininverse-quantization of individual CUs as follows. That is, when a CU tobe reverse-quantized is a selection target CU, the CU decoding section74 obtains a QP value of the selection target CU from the QP differencevalue #73 b of the selection target CU which is received from the CUsetting section 73 and a QP value of a CU reversely quantizedimmediately before. Then, the CU decoding section 74 carries outinverse-quantization at a quantization level corresponding to the QPvalue of the selection target CU.

On the other hand, when the CU to be reverse-quantized is not aselection target CU, the CU decoding section 74 determines QP differencevalues used in inverse-quantization of the CU as follows. That is, whena prediction mode #73 m of the CU which is received from the CU settingsection 73 indicates an inter-prediction image, the CU decoding section74 obtains a QP value of a CU to be reverse-quantized from a QPdifference value #73 b of a selection target CU in the first QP encodingunit region to which the CU belongs and a QP value of a CU reverselyquantized immediately before. Then, the CU decoding section 74 carriesout inverse-quantization at a quantization level corresponding to the QPvalue of the CU.

In contrast thereto, when a prediction mode #73 m of the CU which isreceived from the CU setting section 73 indicates an intra-predictionimage, the CU decoding section 74 obtains a QP value of a CU to bereverse-quantized from a QP difference value #73 b of a selection targetCU in the second QP encoding unit region to which the CU belongs and aQP value of a CU reversely quantized immediately before. Then, the CUdecoding section 74 carries out inverse-quantization at a quantizationlevel corresponding to the QP value of the CU.

The CU decoding section 74 carries out inverse-quantization as above andcarries out DCT reverse-transform to generate predictive residual. Then,the CU decoding section 74 adds the predicted image #75 corresponding tothe encoded data #73 b which is received from the predicted imagegeneration section 75 to the predictive residual to generate a decodedimage #74.

In accordance with the prediction mode #73 m transmitted from the CUsetting section 73, the predicted image generation section 75 generatesan intra-predicted image from the decoded image #74 stored in the framememory 15 or calculates a motion vector using the reference image #74stored in the frame memory 15 and carries out motion compensation basedon the motion vector to generate an inter-predicted image. The predictedimage generation section 75 outputs the generated predicted image #75which is one of the intra-predicted image and the inter-predicted image.

At the time when the decoded image generation process per CU by the CUdecoding section 74 has been made with respect to all CUs constitutingthe encoded data #71 b, the process of generating the decoded image #7corresponding to encoded data inputted to the video decoding device 7 iscompleted.

As described above, the video decoding device decodes encoded data of aQP difference value not with respect to each CU but with respect to onlya selection target CU. Accordingly, it is possible to generate a decodedimage from encoded data with a fewer amount of codes than a conventionalvideo decoding device.

Furthermore, as described above, by introducing the deltaQuantAvailIntraflag, it is possible to prevent the side information determinationsection 81 from repeatedly supplying a QP difference value of theselection target CU to the side information encoding section 82.

(Video Encoding Device)

It is known that in a case where an input image includes a relativelylarge number of regions to be inter-encoded, even when quantization ismade with higher accuracy of QP values due to increased number of QPdifference values, a reduced amount of codes of prediction residual issmaller than an increased amount of codes of the QP difference values,resulting in decrease in encoding efficiency.

The moving image encoding device in accordance with the presentembodiment is designed such that as an input image includes a relativelylarger number of regions to be inter-encoded, the moving image encodingdevice encodes a relatively smaller number of QP difference values. Thatis, as an input image includes a relatively larger number of regions tobe intra-encoded, the moving image encoding device encodes a relativelylarger number of QP difference values.

With reference to drawings, the following details the moving imageencoding device in accordance with the present embodiment.

Initially, an explanation is made as to a configuration of a video imageencoding device 8 in accordance with the present embodiment withreference to FIG. 26. FIG. 26 is a block diagram showing theconfiguration of the video encoding device 8. As shown in FIG. 26, thevideo encoding device 8 includes a side information determinationsection 81, a side information encoding section 82, a CU setting section83, a CU encoding section 84, a variable-length code multiplexingsection 25, a CU decoding section 46, a frame memory 27, and a predictedimage generating section 88. An explanation is made here as to the sideinformation determination section 81, the side information encodingsection 82, and the predicted image generating section 88.

Since the variable-length code multiplexing section 25, the CU decodingsection 46, and the frame memory 27 have been already explained in Firstor Second Embodiment, the following explains other members.

The predicted image generating section 88 generates an intra-predictedimage #88 a from a decoded image #46 stored in the frame memory 27.Furthermore, the predicted image generating section 88 calculates motionvectors by using the reference image #46 and carries out motioncompensation based on the motion vectors, thereby generating aninter-predicted image #88 b.

Furthermore, the predicted image generating section 88 compares theintra-predicted image and the inter-predicted image with an input image#100, selects one of the intra-predicted image and the inter-predictedimage, and outputs the selected image as a predicted image #88.Furthermore, the predicted image generating section 88 outputs aprediction mode #88 m which is information indicating which of theintra-predicted image and the inter-predicted image is selected.

The side information determination section 81 determines sideinformation based on the input image #100 and the prediction mode #88 mregarding each CU, and outputs the determined side information as sideinformation #81. Specifically, the side information determinationsection 81 determines, based on a predetermined algorithm with respectto each slice (or picture), the size of a first QP encoding unit regionand the size of a second QP encoding unit region, and causes sizeinformation indicative of the sizes of the QP encoding unit regions tobe stored in a slice header (picture parameter set) of the sideinformation #81. Here, the side information determination section 81determines the size of the first QP encoding unit region to berelatively larger than the size of the second QP encoding unit region.More specifically, the side information determination section 81determines the sizes of the first QP encoding unit region and the secondQP encoding unit region in such a manner that the first QP encoding unitregion (unit region) consists of a plurality of the second QP encodingunit regions (fourth unit region).

Furthermore, the side information determination section 81 defines thefirst QP encoding unit region and the second QP encoding unit regionconstituting the input image #100 (or individual slices) based on thesize information of the first QP encoding unit region and the size ofthe second QP encoding unit region in the picture parameter set (orslice header), and causes a QP difference value of each CU selected by alater-mentioned process based on the prediction mode #88 m (the CU ishereinafter also referred to as “selection target CU”) to be stored as apart of CU information of the CU in the side information #81.Furthermore, the side information determination section 81 causes theprediction mode #88 m of the CUs to be stored in the side information#81.

The side information encoding section 82 encodes the side information#81 to output side information encoded data #82.

In the process of encoding the side information #81, the sideinformation encoding section 82 encodes the QP difference valuesreceived from the side information determination section 81. The encodedQP difference values constitute a part of the side information encodeddata #82.

Similarly, in the process of encoding the side information #81, the sideinformation encoding section 82 encodes size information of the QPencoding unit regions. The encoded size information constitutes a partof the side information encoded data #82.

Specifically, with respect to each of the first QP encoding unit regionand the second QP encoding unit region, the side information encodingsection 82 applies a logarithmic function with base of 2 to the size ofthe QP encoding unit region and subtracts 4 from the resultant, therebygenerating encoded data of the size information.

The CU setting section 83 divides the input image #100 into a pluralityof slices, divides each slice into a plurality of CUs, and outputs CUimages #83 b regarding individual CUs.

Furthermore, when outputting the CU images #83 b regarding individualCUs, the CU setting section 83 outputs, with respect to a part of theCUs, not only CU images #83 b of the part but also QP difference values#83 of the part which are included in the side information #81.

The CU encoding section 84 carries out DCT with respect to a predictionresidual between sequentially inputted CU images 83 b and a predictedimage transmitted from the predicted image generating section (notshown).

In a case where a predicted image transmitted from the predicted imagegenerating section 88 with respect to the input CU image #83 b is aninter-predicted image (i.e. a case where the prediction mode #88 mtransmitted from the predicted image generating section 88 indicates aninter-prediction mode), the CU encoding section 84 quantizes DCTcoefficients of the prediction residual at a quantization levelcorresponding to a QP value determined by a QP difference value #83 a ofa selection target CU in the first QP encoding unit region to which theCU image #83 b belongs.

On the other hand, in a case where a predicted image transmitted fromthe predicted image generating section 88 with respect to the input CUimage #83 b is an intra-predicted image (i.e. a case where theprediction mode #88 m transmitted from the predicted image generatingsection 88 indicates an intra-prediction mode), the CU encoding section84 quantizes DCT coefficients of the prediction residual at aquantization level corresponding to a QP value determined by a QPdifference value #83 a of a selection target CU in the second QPencoding unit region to which the CU image #83 b belongs.

The CU encoding section 84 outputs, to the variable-length codemultiplexing section 25, CU encoded data #84 obtained by the above DCTand the quantization process.

An explanation was made above as to the configuration of the videoencoding device 8. An explanation will be made below as to a specificprocess carried out by the side information determination section 81 andthe side information encoding section 82.

Based on the side information #81, the side information determinationsection 81 refers to, in raster scan order, a skip flag of one or moreCUs constituting the whole of each first QP encoding unit region. Withrespect to each first QP encoding unit region, the CU setting section 83calculates a QP difference value #83 a which is a difference between aQP value of a CU whose skip flag of “0” is referred to for the firsttime in the first QP encoding unit region (selection target CU) and adefault QP value.

Furthermore, accompanying the above process for referring to the skipflag of each CU, the side information determination section 81 isdesigned to judge whether the CU is positioned at the upper left end ofthe second QP encoding region and a prediction mode #88 m for the CUthat is transmitted from the predicted image generating section is anintra-prediction mode (i.e. the result of the judgment process is true).When judging that the result of the judgment process with respect to theCU is true, the side information determination section 81 calculates theQP difference value #83 a which is a difference between the QP value ofthe CU (selection target CU) and the QP default value.

Then, the side information determination section 81 supplies the QPdifference value of each selection target CU to the CU setting section83 and the side information encoding section 82.

The side information encoding section 82 encodes each QP differencevalue received from the side information determination section 81, andgenerates encoded data of each QP difference value as a part of theencoded data #82.

Specifically, the side information determination section 81 and the sideinformation encoding section 82 sequentially carries out a processmentioned below with respect to each CU by using a coding unit syntaxshown in FIG. 27. That is, as is seen from FIG. 27, when x-component andy-component of the upper left coordinates of a CU whose skip flag(skip_flag) is referred to are equal to integer-multiples of the size ofthe first QP encoding unit region (MinDeltaQuantCodingUnitSize), theside information determination section 81 sets the value ofdeltaQuantAail to “true”.

Then, the side information determination section 81 refers to the valueof each skip flag, and when referring to a skip flag whose value is “0”,the side information determination section 81 sets the flag indicativeof whether a QP difference value is encodable or not in intra-encoding aCU image (deltaQuantAvailIntra) to “true”. Furthermore, when referringto a skip flag whose value is “0” while the value of deltaQuantAvail is“true”, the side information determination section 81 supplies, to theside information encoding section 82, the QP difference value of the CUwhose skip flag has been referred to, as a part of the side information#81. The side information encoding section 82 carries out an encodingprocess with respect to the QP difference value, and sets the values ofdeltaQuantAvail and deltaQuantAvailIntra to “false”.

Furthermore, also when x-component and y-component of the upper leftcoordinates of a CU whose skip flag (skip_flag) is referred to are equalto integer-multiples of the size of the second QP encoding unit region(MinDeltaQuantCodingUnitSize) and the value of deltaQuantAvailIntra is“true”, the side information determination section 81 supplies, to theside information encoding section 82, the QP difference value of the CUwhose skip flag has been referred to, as a part of the side information#81.

As a result of the above processes by the side information determinationsection 81 and the side information encoding section 82, thevariable-length code multiplexing section 25 receives, from the sideinformation encoding section 82, side information encoded data #82including encoded data of i) the QP difference value of the selectiontarget CU and ii) size information of the first QP encoding unit regionand the second QP encoding unit region that is determined with respectto each picture (or each slice constituting a picture). Furthermore, thevariable-length code multiplexing section 25 multiplexes CU encoded data#84 received from the CU encoding section 84 with the side informationencoded data #82, thereby generating encoded data #8 and outputting it.When x-component and y-component of the upper left coordinates of a CUwhose skip flag (skip_flag) is referred to are equal tointeger-multiples of the size of the first QP encoding unit region(MinDeltaQuantCodingUnitSize), the value of deltaQuantAail is set to“true”.

Then, when referring to a skip flag with the value of “0” while thevalue of deltaQuantAvail is “true”, the side information determinationsection 81 calls up the transform_tree syntax shown in FIG. 21 andrefers to the value of residualDataPresentFlag. When the value ofresidualDataPresentFlag is “0”, the side information determinationsection 61 calls up a coding unit syntax with respect to the next CU.

In the above explanation, judgment is made when x-component andy-component of the upper left coordinates of a CU are equal tointeger-multiples of the size of a QP encoding unit region(MinDeltaQuantCodingUnitSize). Alternatively, other method for judging aCU of the same position may be employed. For example, judgment may bemade by using a CU coordinates index shown below. The CU coordinatesindex is an index which indicates the position of a CU obtained bydividing an LCU as small as possible and which increases as 0, 1, 2 inthe order of raster scan decoding from the upper left of the LCU. Alsowhen an LCU is not divided as small as possible, it is possible toassign a CU coordinates index to a corresponding position with respectto each CU. In a case where the minimum CU size is 4×4 blocks, judgmentbased on the CU coordinates index being 0, 4, 8, and 12 for exampleallows MinDeltaQuantCodingUnitSize to be 8, i.e. the QP encoding unitregion to be 8×8.

In the above embodiment, an explanation was made as to a case wherex-component and y-component of the upper left coordinates of a CU areequal to integer-multiples of the size of a QP encoding unit region(MinDeltaQuantCodingUnitSize). Alternatively, different sizes of a QPencoding unit region may be used for x-component and y-component. Inthis case, judgment is made based on, for example, x-component of theupper left coordinates of a CU being equal to an integer-multiple of thewidth of a QP encoding unit region (MinDeltaQuantCodingUnitWidth) andy-component of the upper left coordinates of the CU being equal to aninteger-multiple of the height of the QP encoding unit region(MinDeltaQuantCodingUnitHeight).

(Additional Matter)

In the above embodiment, an explanation was made as to a case where theside information determination section 81 determines a selection targetCU according to the coding unit syntax shown in FIG. 27, and the sideinformation encoding section 82 encodes a QP difference value of theselection target CU according to the coding unit syntax shown in FIG.27. The corresponding video image decoding device is designed such thatthe side information decoding section 72 decodes a QP difference valueof the selection target CU according to the coding unit syntax shown inFIG. 27. However, the present invention is not limited to this. That is,the side information determination section 81 may determine theselection target CU according to the coding unit syntax shown in FIG.28. The corresponding video image decoding device is designed such thatthe side information decoding section 72 decodes a QP difference valueof the selection target CU according to the coding unit syntax shown inFIG. 28.

That is, instead of the coding unit shown in FIG. 27, there may beprovided a syntax for carrying out a diverging process according to theprediction mode of a CU. Specifically, as in the case of coding unitsyntax shown in FIG. 28, cu_qp_delta to be referred to when the sideinformation encoding section 82 encodes or the side information decodingsection 72 decodes may be described at different positions depending onwhether the prediction mode of a CU is an intra-prediction mode, aninter-prediction mode, a merge mode, or a direct mode (in other words,the step of encoding cu_qp_delta by the side information encodingsection 82 may be a step following encoding of the prediction mode of aCU and may vary in whether encoding of cu_qp_delta is made depending onthe kind of the prediction mode. The step of decoding cu_qp_delta by theside information decoding section 72 is a step following decoding of theprediction mode of a CU and may vary with respect to each predictionmode).

As is seen from the coding unit syntax shown in FIG. 28, the presentinvention may be arranged such that in a case where the prediction modeis a skip mode, the QP difference value is not encoded, in a case wherethe prediction mode is an intra-prediction mode, the QP difference valueis encoded only for a CU whose size is not less thanMinIntraDeltaCodingUnitSize, and in a case where the prediction mode isneither the intra-prediction mode nor the skip mode, the QP differencevalue is encoded only for a CU whose size is not less thanMinDeltaCodingUnitSize.

(Additional Matter)

In the above embodiment, a QP value (cu_qp) of a CU to be quantized isobtained by adding a QP value referred to immediately before (pred_qp)and a QP difference value of the CU to be quantized. Here, the QP valuereferred to immediately before (QP predicted value) may be a QP value ofa CU at the left side of the CU to be quantized, or may be a QP value ofa CU positioned immediately before the CU to be quantized in the rasterscan order. Alternatively, the QP value referred to immediately beforemay be the average of a QP value of a CU at the left side of the CU tobe quantized and a QP value of a CU at the upper side of the CU to bequantized.

Fifth Embodiment (Video Decoding Device)

A video decoding device in accordance with the present embodiment is adevice for decoding encoded data #10 from a video encoding device 10(which will be explained below) to generate a decoded image #9. FIG. 31shows an example of coding_unit syntax included in the encoded data #10.

The following details the video decoding device in accordance with thepresent embodiment with reference to drawings.

Initially, an explanation is made as to a configuration of the videodecoding device in accordance with the present embodiment with referenceto FIG. 29. FIG. 29 is a block diagram showing the configuration of thevideo decoding device 9. As shown in FIG. 29, the video decoding device9 includes a variable-length code inverse-multiplexing section 91, aside information decoding section 92, a CU setting section 93, a CUdecoding section 94, and a frame memory 15.

The encoded data #10 inputted to the video decoding device 9 is inputtedto the variable-length code inverse-multiplexing section 91. Thevariable-length code inverse-multiplexing section 91 reverse-multiplexesthe input encoded data #9 so as to divide the encoded data #9 into sideinformation encoded data #91 a which is encoded data regarding sideinformation and encoded data #91 b which is encoded data regarding apicture, and outputs the side information encoded data #91 a and theencoded data #91 b to the side information decoding section 92 and theCU setting section 93, respectively.

The side information decoding section 92 decodes the side informationencoded data #91 a to generate side information #92, and outputs theside information #92 to the CU setting section 93.

When decoding the side information encoded data #91 a, the sideinformation decoding section 92 decodes encoded data of size informationindicative of the size of a QP encoded unit region, thereby generatingthe size information as a part of the side information #92.

Furthermore, when decoding the side information encoded data #91 a, theside information decoding section 92 decodes, for each LCU, encoded dataof a QP difference value of each QP encoding unit region constitutingthe LCU or decodes encoded data of a QP difference value of the LCU,thereby generating the QP difference value as a part of the sideinformation #92.

The following more specifically describes the QP difference valuedecoding process carried out by the side information decoding section92.

The side information decoding section 92 decodes size information(MinDeltaQuantCodingUnitSize) included in a slice header (pictureparameter set) of the encoded data #10 so as to determine a(longitudinal and lateral) size of a QP encoding unit region.

Further, the side information decoding section 92 decodes adeltaQuantAvailCU flag of each LCU.

In a case where a value of deltaQuantAvailCU of the LCU is “false”, theside information decoding section 92 determines to decode, per LCU, a QPdifference value used in quantization of the LCU (decode one QPdifference value at most in the LCU). Then, the side informationdecoding section 92 utilizes the QP difference value to decode each CUincluded in the LCU.

On the other hand, in a case where the value of deltaQuantAvailCU of theLCU is “true”, the side information decoding section 92 determines todecode, per CU, a QP difference value used in quantization of the LCU.Then, the side information decoding section 92 decodes a QP differencevalue of a selection target CU. Note that one selection target CU atmost is selected for each QP encoding unit region.

With reference to the coding_unit syntax of FIG. 31, the followingdescribes specific processes carried out by the side informationdecoding section 92 with respect to each LCU.

The side information decoding section 92 carries out the followingprocesses with respect to a target CU of each of at least one CUconstituting a LCU.

In a case where the target CU is a CU located on an upper left end ofthe LCU (i.e., in a case where x-component and y-component of an upperleft coordinate of the target CU are integer-multiples ofmax_coding_unit_width and max_coding_unit_height, respectively), theside information decoding section 92 sets a deltaQuantAvailLCU flag to“true”. In a case where the target CU is located on an upper left end ofa QP encoding unit region to which the target CU belongs (i.e.,x-component and y-component of an upper left coordinate of the target CUare integer-multiples of MinDeltaQuantCodingUnitSize) and where thedeltaQuantAvailCU flag is “true”, the side information decoding section92 sets a deltaQuantAvail flag to “true”. The deltaQuantAvailLCU flag,the deltaQuantAvailCU flag, and the deltaQuantAvail flag have thefollowing meanings. The deltaQuantAvailLCU flag is a flag forcontrolling encoding/decoding of the deltaQuantAvailCU flag encoded perLCU, and indicates whether the deltaQuantAvailCU can be encoded ordecoded. The deltaQuantAvailCU flag is a flag for selecting whether a QPdifference value is encoded per LCU or encoded per CU. ThedeltaQuantAvailCU flag becomes “false” in a case where a QP differencevalue is encoded per LCU, and becomes “true” in a case where a QPdifference value is encoded per CU. The deltaQuantAvail flag is a flagfor controlling a QP encoding unit in a case where a QP difference valueis encoded per CU, and indicates whether qp_delta can be encoded ordecoded.

Furthermore, in a case where a value of a skip flag of the target CU is“0” and where the deltaQuantAvailLCU flag is “true”, the sideinformation decoding section 92 decodes qp_delta of the target CU (i.e.,selection target CU), and sets decoded qp_delta as the QP differencevalue of the target CU. Moreover, the side information decoding section92 decodes the deltaQuantAvailCU flag, and sets the deltaQuantAvailLCUflag to “false”. According to the syntax of FIG. 31, thedeltaQuantAvailCU flag follows qp_delta. Note, however, that it is alsopossible to employ a syntax in which the deltaQuantAvailCU flag isfollowed by qp_delta.

Also in a case where the value of the skip flag of the target CU is “0”and where the deltaQuantAvail flag is “true”, the side informationdecoding section 92 decodes qp_delta of the target CU (i.e., selectiontarget CU), and sets decoded qp_delta as the QP difference value of thetarget CU. Further, the side information decoding section 92 sets thedeltaQuantAvail flag to “false”.

As is clear from the above description and the coding_unit syntax ofFIG. 31, the deltaQuantAvail flag cannot be “true” as long as thedeltaQuantAvailCU flag of an LCU is “false”. Accordingly, a QPdifference value of a single CU in which a skip flag “0” is referred tofirst in raster scan order in an LCU is decoded. Consequently, in a casewhere the deltaQuantAvailCU flag is “false”, a QP difference value isdecoded per LCU.

On the other hand, in a case where the deltaQuantAvailCU flag of the LCUis “true”, the deltaQuantAvail flag becomes “true” every time thecoding_unit syntax of FIG. 31 is applied to the target CU located on theupper left end of the QP encoding unit region. Accordingly, a QPdifference value of a selection target CU is decoded. Note that oneselection target CU at most is selected for each QP encoding unitregion.

Further, as is clear from the coding_unit syntax of FIG. 31, whendecoding a QP difference value of a CU in an LCU in which CU a skip flag“0” is referred to first, it is determined whether or not a QPdifference value of a CU that is referred to later in the LCU isdecoded.

In accordance with the input side information #92, the CU settingsection 93 divides the encoded data #91 b into a plurality of slices,divides each slice into a plurality of QP encoding unit regions,separates each QP encoding unit region into encoded data #93 bcorresponding to individual CUs, and outputs the encoded data #93 bsequentially to the CU decoding section 94.

Further, the CU setting section 93 refers to the deltaQuantAvailCU flagfor each LCU. The deltaQuantAvailCU flag is a flag indicative of whethera QP difference value is encoded per LCU or an LCU is encoded per QPencoding region unit. In a case where the deltaQuantAvailCU flag of theLCU is “true”, the CU setting section 93 refers to CU information ofeach CU belonging to the LCU and, as to CUs whose CU informationcontains a QP difference value, outputs the QP difference value to theCU decoding section 94.

On the other hand, in a case where the deltaQuantAvailCU flag of the LCUis “false”, the CU setting section 93 outputs, to the CU decodingsection 94, a QP difference value contained in CU information of theLCU.

Furthermore, the CU setting section 93 outputs, to the CU decodingsection 94, the deltaQuantAvailCU flag of each LCU.

The CU decoding section 94 sequentially decodes and reverse-quantizesthe encoded data #93 b corresponding to inputted CUs(inverse-quantization unit region), respectively, thereby generating andoutputting decoded images #94 corresponding to the CUs, respectively.The decoded images #94 are also outputted to the frame memory 15.

Specifically, when decoding and reverse-quantizing encoded data #93 bcorresponding to a CU, the CU decoding section 94 obtains, in accordancewith a value of the deltaQuantAvailCU flag of an LCU to which the CUbelongs, a QP value from a QP difference value #93 a of a QP encodingunit region to which the CU belongs or from a QP difference value #93 aof the LCU, and carries out the inverse-quantization in accordance withthe QP value.

At the time when the decoded image generation process per CU by the CUdecoding section 94 has been made with respect to all CUs constitutingthe encoded data #91 b, the process of generating the decoded image #9corresponding to encoded data inputted to the video decoding device 9 iscompleted.

As described above, the video decoding device decodes encoded data of aQP difference value not with respect to each CU but with respect to eachLCU unit or each QP encoding unit region constituting an LCU, andaccordingly can generate a decoded image from encoded data with thesmaller amount of codes than a conventional art.

(Video Encoding Device)

A video encoding device in accordance with the present embodimentcarries out a process of dividing each LCU constituting the input imageinto a plurality of CUs (Coding Unit: quantization unit region) by usinga coding_tree syntax described in JCTVC-C403, as in the video encodingdevice in accordance with Second Embodiment. Note, however, that thesyntax described in the present embodiment is one obtained by partlysimplifying the syntax described in JCTVC-C403 (the same applies to theother embodiments using the coding_tree syntax).

However, differently from the video encoding device in accordance withSecond Embodiment, the video encoding device in accordance with thepresent embodiment is arranged such that it is determined based on adeltaQuantAvailCU flag (described later) whether a QP difference valueused in quantization of each LCU constituting an input image is encodedper LCU or per QP encoding region constituting the LCU.

The following details the video encoding device in accordance with thepresent embodiment with reference to drawings.

Initially, an explanation is made as to a configuration of a videoencoding device 10 in accordance with the present embodiment withreference to FIG. 30. FIG. 30 is a block diagram showing a configurationof the video encoding device 10. As shown in FIG. 30, the video encodingdevice 10 includes a side information determination section 101, a sideinformation encoding section 102, a CU setting section 43, a CU encodingsection 44, a variable-length code multiplexing section 25, a CUdecoding section 46, and a frame memory 27.

The side information determination section 101 determines sideinformation in accordance with an input image #100, and outputs thedetermined side information as side information #101.

Specifically, the side information determination section 101 determinesthe (longitudinal and lateral) size of a QP encoding unit region, andcauses size information (MinDeltaQuantCodingUnitSize) indicative of thesize of the QP encoding unit region to be stored in a slice header(picture parameter set) of the side information #101.

Further, the side information determination section 101 decodes adeltaQuantAvailCU flag of each LCU constituting the input image #100which flag is determined according to a predetermined algorithm.

In a case where a value of the deltaQuantAvailCU flag of the LCU is“false”, the side information determination section 101 determines toencode, per LCU, a QP difference value used in quantization of the LCU(i.e., encodes one QP difference value at most in the LCU). Then, theside information determination section 101 causes the QP differencevalue to be stored in CU information of an LCU constituting the sideinformation #101.

On the other hand, in a case where the value of the deltaQuantAvailCUflag of the LCU is “true”, the side information determination section101 determines to encode, per CU, a QP difference value used inquantization of the LCU. Then, the side information determinationsection 101 causes a QP difference value of a selection target CU to bestored in CU information of the selection target CU constituting theside information #101. Note that one selection target CU at most isselected for each QP encoding unit region.

The side information encoding section 102 encodes the side information#101 and outputs side information encoded data #102. The sideinformation encoded data #102 is supplied to the variable-length codemultiplexing section 25. When encoding the side information #101, theside information encoding section 102 encodes each QP difference valueand the size information.

Note that the CU setting section 43, the CU encoding section 44, the CUdecoding section 46, the variable-length code multiplexing section 25,and the frame memory 27 have been described in First or SecondEmbodiment, and therefore are not described here repeatedly.

An explanation was made above as to the configuration of the videoencoding device 10. An explanation is made below, with reference to thecoding_unit syntax of FIG. 31, as to a specific process carried out bythe side information determination section 101 and the side informationencoding section 102 with respect to each LCU constituting the inputimage #100.

The side information determination section 101 carries out the followingprocesses with respect to a target CU of each of at least one CUconstituting an LCU.

In a case where the target CU is a CU located on an upper left end ofthe LCU (i.e., in a case where x-component and y-component of an upperleft coordinate of the target CU are integer-multiples ofmax_coding_unit_width and max_coding_unit_height, respectively), theside information determination section 101 sets a deltaQuantAvailLCUflag to “true”. In a case where the target CU is located on an upperleft end of a QP encoding unit region to which the target CU belongs(i.e., x-component and y-component of the upper left coordinate of thetarget CU are integer-multiples of MinDeltaQuantCodingUnitSize) andwhere a deltaQuantAvailCU flag is “true”, the side informationdetermination section 101 sets a deltaQuantAvail flag to “true”.

Furthermore, in a case where a value of a skip flag of the target CU is“0” and where the deltaQuantAvailLCU flag is “true”, the sideinformation determination section 101 causes a QP difference value ofthe target CU (i.e., selection target CU) to be stored in CU informationof the target CU, decodes the deltaQuantAvailCU flag, and sets thedeltaQuantAvailLCU flag to “false”.

Also in a case where the value of the skip flag of the target CU is “0”and where the deltaQuantAvail flag is “true”, the side informationdetermination section 101 causes a QP difference value of the target CU(i.e., selection target CU) to be stored in CU information of the targetCU and sets the deltaQuantAvail flag to “false”.

The QP difference value thus stored in the CU information is supplied,as part of the side information #101, to the side information encodingsection 102 along with the deltaQuantAvail flag of the LCU.

The side information encoding section 102 encodes the side information#101 so as to generate side information encoded data #102, and suppliesthe side information encoded data #102 to the variable-length codemultiplexing section 25.

As is clear from the above description and the coding_unit syntax ofFIG. 31, the deltaQuantAvail flag cannot be “true” as long as thedeltaQuantAvailCU flag of the LCU is “false”. Accordingly, a QPdifference value is stored in CU information of a single CU in which askip flag “0” is referred to first in raster scan order in the LCU.Consequently, in a case where the deltaQuantAvailCU flag is “false”, aQP difference value is encoded per LCU.

On the other hand, in a case where the deltaQuantAvailCU flag of the LCUis “true”, the deltaQuantAvail flag becomes “true” every time thecoding_unit syntax of FIG. 31 is applied to the target CU located on theupper left end of the QP encoding unit region. Accordingly, a QPdifference value of a selection target CU is encoded. Note that oneselection target CU at most is selected for each QP encoding unitregion.

Further, as is clear from the coding_unit syntax of FIG. 31, whenencoding a QP difference value of a CU in which a skip flag “0” isreferred to first in an LCU, it is determined whether or not a QPdifference value of a CU referred to later in the LCU is encoded.

As a result of the processes carried out by the side informationdetermination section 101 and the side information encoding section 102,the variable-length code multiplexing section 25 receives, from the sideinformation encoding section 102, side information encoded data #102including encoded data of (i) a QP difference value determined per LCUor QP encoding unit region, (ii) size information of the QP encodingunit regions determined with respect to each picture parameter set (eachslice), and (iii) a deltaQuantAvailCU flag. Furthermore, thevariable-length code multiplexing section 25 multiplexes CU encoded data#44 received from the CU encoding section 44 and the side informationencoded data #102 to generate and output encoded data #10.

Sixth Embodiment (Video Decoding Device)

The video decoding device in accordance with the present embodiment is adevice for decoding encoded data #112 supplied from the video encodingdevice 112 (which will be explained below) to generate a decoded image#111. FIG. 34 illustrates an example of a coding_unit syntax containedin the encoded data #112.

The following details the video decoding device in accordance with thepresent embodiment, with reference to drawings.

First described is a configuration of the video decoding device inaccordance with the present embodiment, with reference to FIG. 32. FIG.32 is a block diagram showing the configuration of a video decodingdevice 111. As shown in FIG. 32, the video decoding device 111 includesa variable-length code inverse-multiplexing section 1111, a sideinformation decoding section 1112, a CU setting section 1113, a CUdecoding section 1114, and a frame memory 15.

The encoded data #112 inputted to the video decoding device 111 isreceived by the variable-length code inverse-multiplexing section 1111.The variable-length code inverse-multiplexing section 1111reverse-multiplexes the inputted encoded data #112 so as to divide theencoded data #112 into (i) side information encoded data #1111 a whichis encoded data regarding side information and (ii) encoded data #1111 bwhich is encoded data regarding a picture, and outputs the sideinformation encoded data #1111 a and the encoded data #1111 b to theside information decoding section 1112 and the CU setting section 1113,respectively.

The side information decoding section 1112 decodes the side informationencoded data #1111 a to generate side information #1112, and outputs theside information #1112 to the CU setting section 1113.

In the process of decoding the side information encoded data #1111 a,the side information decoding section 1112 decodes encoded data of sizeinformation indicative of sizes of QP encoding unit regions of a I sliceQP encoding unit region, a Q slice encoding unit region, and a P sliceencoding unit region. This generates the size information which servesas a part of the side information #1112.

Moreover, in the process of decoding the side information encoded data#1111 a, the side information decoding section 1112 decodes, for each ofthe LCU, the encoded data of QP differential values of subject QPencoding unit regions that configure that LCU. This as a resultgenerates a QP differential value which serves as a part of the sideinformation #1112. In the embodiment, the side information decodingsection 1112 recognizes, for every subject QP encoding unit region thatconfigure the LCU, which of the three types of QP encoding unit regionsthe subject QP encoding unit region corresponds to, by referring to aslice type inside the slice header of a slice to which the LCU belongs.

The following details the decoding process of the QP difference value bythe side information decoding section 1112.

The side information decoding section 1112 defines, for each of the LCUsthat are subjected to the quantization process, a QP encoding unitregion (also called “subject QP encoding unit region”) of any one of thethree QP encoding unit regions (I slice QP encoding unit region, Q sliceQP encoding unit region, and B slice QP encoding unit region) that areof different sizes in accordance with the slice type of the slice towhich that LCU belongs. For example, when the slice type of the slice towhich the LCU belongs is I slice, the side information decoding section1112 defines the I slice QP encoding unit region as the subject QPencoding unit region.

Thereafter, for each of the defined subject QP encoding unit regions,the side information decoding section 1112 refers to skip flags of oneor more CU that configures the whole subject QP encoding unit region, inraster scanning order. For each of the subject QP encoding unit regions,the side information decoding section 1112 decodes cu_qp_delta (see FIG.34) of a CU whose skip flag having a value of “0” is referred to in thatQP encoding unit region for the first time, and sets this decodedcu_qp_delta as the QP difference value for that CU.

Specifically, the side information decoding section 1112 sequentiallysubjects every CU to a process below by use of a coding unit syntax (seeFIG. 34). That is, when x-component and y-component of upper leftcoordinates of a CU whose skip flag (skip_flag) is referred to areinteger-multiples of the size of the subject QP encoding unit region(MinlDeltaQuantCodingUnitSize when the slice type of the slice to whichthe LCU belongs is I slice; MinBDeltaQuantCodingUnitSize andMinPDeltaQuantCodingUnitSize when the slice types are B slice and Pslice, respectively), the side information decoding section 1112 setsthe value of a flag indicative of whether decoding is possible or not(deltaQuantAvail) to “true”. Then, when the side information decodingsection 1112 refers to a skip flag “0” while the value ofdeltaQuantAvail is “true”, the side information decoding section 1112decodes the cu_qp_delta of the CU to which the skip flag was referred,and sets the decoded cu_qp_delta as the QP difference value for that CU.Thereafter, the side information detecting section 1112 sets the valueof deltaQuantAvail to “false”.

In accordance with the input side information #1112, the CU settingsection 1113 divides the encoded data #1111 b into a plurality ofslices, divides each slice into a plurality of subject QP encoding unitregions, separates each subject QP encoding unit region into encodeddata #1113 b corresponding to individual CUs, and outputs the encodeddata #1113 b sequentially to the CU decoding section 1114.

The CU decoding section 1114 sequentially decodes and reverse-quantizesthe encoded data #1113 b corresponding to inputted individual CUs(reverse-quantized unit region) to generate decoded images #1114corresponding to individual CUs and outputs the decoded images #1114.The decoded images #1114 are outputted to the frame memory 15, too.

Specifically, when decoding and reverse-quantizing the encoded data#1113 b corresponding to a CU, the CU decoding section 1114 obtains a QPvalue from the QP difference value #1113 a of the subject QP encodingunit region to which the CU belongs, to carry out theinverse-quantization process.

Once the decoded image generation process by the CU decoding section1114 with respect to each CU is completed for all CUs configuring theencoded data #1111 b, the process of generating the decoded image #111corresponding to encoded data inputted to the video decoding device 111is completed.

As described above, the video decoding device decodes encoded data of aQP difference value not with respect to each CU but with respect to eachsubject QP encoding unit region determined in accordance with the slicetype of the slice to which the CU belongs. Accordingly, the videodecoding device can generate a decoded image from encoded data having asmaller amount of codes than conventional art.

(Video Encoding Device)

A video encoding device 112 in accordance with the present embodiment isconfigured so that the video encoding device 112 encodes a QP differencevalue of different granularities (numbers) between cases in which theslice configuring the input image includes (i) a large number of Islices, (ii) a large number of P slices, or (iii) a large number of Bslices.

The following describes the video encoding device 112 in accordance withthe present embodiment, with reference to FIG. 33. FIG. 33 is a blockdiagram showing a configuration of the video encoding device 112. Asshown in FIG. 33, the video encoding device 112 includes a sideinformation determination section 1121, a side information encodingsection 1122, a CU setting section 43, a CU encoding section 44, avariable-length code multiplexing section 25, a CU decoding section 46,and a frame memory 27.

The CU setting section 43, the CU encoding section 44, thevariable-length code multiplexing section 25, the CU decoding section46, and the frame memory 27 have already been explained in First orSecond Embodiment, and therefore the following description deals withthe side information determination section 1121 and the side informationencoding section 1122.

The side information determination section 1121 defines any one of a QPencoding unit region (also called “subject QP coding unit region”) ofthree QP encoding unit regions (I slice QP encoding unit region, Q sliceQP encoding unit region, and B slice QP encoding unit region), which areof different size in accordance with the slice type of the slice towhich a respective LCU belongs, for each of LCU that is subject to aquantization process. For example, in a case in which the slice type ofthe slice to which the LCE belongs is an I slice, the side informationdetermination section 1121 defines, as the subject QP encoding unitregion, the I slice QP encoding unit region.

Thereafter, the side information determination section 1121 refers toskip flags of each of at least one CU that configures the whole of eachof the subject QP encoding unit regions defined by the side informationdetermination section 1121, in raster scanning order. For each of thesubject QP encoding unit regions, the side information determinationsection 1121 calculates a QP value of a CU whose skip flag having avalue of “0” is referred to in the QP encoding unit region for the firsttime, and outputs, to the side information encoding section 1122, as apart of the side information, a QP difference value between thiscalculated QP value and a QP value referred to immediately before (ordefault QP value).

Specifically, the side information decoding section 1121 and the sideinformation encoding section 1122 sequentially subject the CUs to aprocess described below by use of a coding unit syntax shown in FIG. 34.That is, when x-component and y-component of the upper left coordinatesof a CU whose skip flag (skip_flag) is referred to are integer-multiplesof the size of the subject QP encoding unit region(MinlDeltaQuantCodingUnitSize when the slice type of the slice to whichthe LCU belongs is I slice; MinBDeltaQuantCodingUnitSize andMinPDeltaQuantCodingUnitSize when the slice types are B slice and Pslice, respectively), the side information decoding section 1121 setsthe value of a flag indicative of whether encoding is possible or not(deltaQuantAvail) to “true”. Then, when the side information decodingsection 1121 refers to a skip flag “0” while the value ofdeltaQuantAvail is “true”, the side information decoding section 1121supplies the QP difference value of the CU to which the skip flag wasreferred, to the side information encoding section 1122 as a part of theside information #41. The side information encoding section 1122executes the encoding process to the QP difference value, and sets thevalue of deltaQuantAvail to “false”.

As a result of the processes carried out by the side informationdetermination section 1121 and the side information encoding section1122, the variable-length code multiplexing section 25 receives, fromthe side information encoding section 1122, side information encodeddata #1122 including encoded data of (i) size information of the threetypes of QP encoding unit regions and (ii) QP difference values of eachof the subject QP encoding unit regions. Furthermore, thevariable-length code multiplexing section 25 multiplexes CU encoded data#44 received from the CU encoding section 44 and the side informationencoded data #1122, to generate and output encoded data #112.

(Additional Matter)

Although the video encoding device 112 is configured so as to encode aQP difference value of different granularities (numbers) between casesin which the slice configuring the input image includes (i) a largenumber of I slices, (ii) a large number of P slices, or (iii) a largenumber of B slices, the present invention is not limited to this Namely,the video encoding device may be configured in such a manner that thegranularity (number) of the QP difference values to be encoded may beabout the same between the case in which the slice includes a largenumber of P slices and the case in which the slice includes a largenumber of B slices. That is to say, each of the values ofMinIDeltaQuantCodingUnitSize,

MinBDeltaQuantCodingUnitSize, and MinPDeltaQuantCodingUnitSize may beset to satisfy the following formula:

[Mathematical Formula 3]

MinDeltaQuantCodingUnitSize=max_coding_unit_width>>log2_min_delta_quant_unit_size_to_lcu  Formula2

Moreover, the MinlDeltaQuantCodingUnitSize, MinBDeltaQuantCodingUnitSize, and MinPDeltaQuantCodingUnitSiz e may beconfigured as a picture parameter set, a segue nce parameter set, or aconfiguration in which the value is encoded inside the encoded data by aslice header or the like.

Seventh Embodiment (Video Decoding Device)

A video decoding device in accordance with the present embodiment is adevice for decoding encoded data #114 supplied from a video encodingdevice 114 (later described) to generate decoded images #113.

The following details the video decoding device in accordance with thepresent embodiment with reference to drawings.

Initially, with reference to FIG. 35, an explanation is made as to aconfiguration of the video decoding device in accordance with thepresent embodiment. FIG. 35 is a block diagram showing the configurationof a video decoding device 113. As shown in FIG. 35, the video decodingdevice 113 includes a variable-length code inverse-multiplexing section1131, a side information decoding section 1132, a CU setting section1133, a CU decoding section 1134, and a frame memory 15.

The encoded data #114 inputted to the video decoding device 113 isinputted to the variable-length code inverse-multiplexing section 1131.The variable-length code inverse-multiplexing section 1131reverse-multiplexes the inputted encoded data #114 so as to divide theencoded data #114 into (i) side information encoded data #1131 a whichis encoded data regarding side information and (ii) encoded data #1131 bwhich is encoded data regarding a picture, and outputs the sideinformation encoded data #1131 a and the encoded data #1131 b to theside information decoding section 1132 and the CU setting section 1133,respectively.

The side information decoding section 1132 decodes the side informationencoded data #1131 a to generate side information #1132 and outputs theside information #1132 to the CU setting section 1133.

In the process for decoding the side information encoded data #1131 a,the side information decoding section 1132 decodes encoded data of sizeinformation indicative of the size of a QP encoding unit region, therebygenerating the size information which serves as a part of sideinformation #1132.

In the process for decoding the side information encoded data #1131 a,the side information decoding section 1132 decodes encoded data of atransform rule index of each slice header, thereby generating thetransform rule index as a part of the side information #1132. Note thatthe transform rule index is an index for identifying each transform ruleexplained in First Embodiment.

Further, in the process for decoding the side information encoded data#1131 a, the side information decoding section 1132 decodes encoded dataof an index (qp_delta_index) of each QP encoding unit region, therebygenerating the index as a part of the side information #1132.

In accordance with the input side information #1132, the CU settingsection 1133 (i) divides the encoded data #1131 b into a plurality ofslices, (ii) divides each slice into a plurality of QP encoding unitregions, (iii) divides each QP encoding unit region into a plural piecesof encoded data #1133 b corresponding to respective CUs, and (iv)sequentially outputs the plural pieces of encoded data #1133 b to the CUdecoding section 34. With respect to each QP encoding unit region, theCU setting section 1133 calculates a QP difference value, which is to beoutputted to the CU decoding section 1134, from an index of the QPencoding unit region contained in the side information #1132 with theuse of a transform rule specified by a transform rule index that is alsocontained in the side information #1132. In addition to the pluralpieces of encoded data #1133 b corresponding to respective CUs in the QPencoding unit region, the CU setting section 1133 outputs, to the CUdecoding section 1134, a QP difference value #1133 a calculated with theuse of the transform rule.

The CU decoding section 1134 sequentially decodes and reverse-quantizesthe inputted plural pieces of encoded data #1133 b corresponding to therespective CUs (reverse-quantization unit region), thereby generatingand outputting decoded images #1134 corresponding to the respective CUs.The decoded images #1134 are also outputted to the frame memory 15.

Specifically, when decoding and reverse-quantizing encoded data #1133 bcorresponding to a CU, the CU decoding section 1134 obtains a QP valuefrom the QP difference value #1133 a of the QP encoding unit region towhich the CU belongs, and carries out an inverse-quantization process.

At a time when the decoded image generation processes, which are carriedout by the CU decoding section 1134 with respect to all the respectiveCUs constituting the encoded data #1131 b, are completed, a process ofgenerating the decoded image #113 corresponding to encoded data inputtedto the video decoding device 113 is completed.

As described above, the video decoding device decodes encoded data of anindex which is smaller in value than a QP difference value (or is mostlysmaller than the QP difference value as shown in (d) of FIG. 8), insteadof decoding encoded data of a QP difference value for each QP encodingunit region. This allows a reduction in amount of codes of encoded data,as a whole, which is received for generating a QP difference value, evenif the amount of codes is increased due to encoding of a transform ruleindex. Accordingly, the video decoding device can generate a QPdifference value from encoded data having the smaller data amount.

(Video Encoding Device)

A video encoding device in accordance with the present embodimentcarries out a process of dividing each of LCUs constituting an inputimage into a plurality of CUs (Coding Unit: quantization unit region) byusing coding_tree syntax described in JCTVC-C403, as with the videoencoding device in accordance with Second Embodiment.

Furthermore, the video encoding device in accordance with the presentembodiment is designed to encode size information indicative of the sizeof a QP encoding unit region.

On the other hand, unlike the video encoding device in accordance withSecond Embodiment, the video encoding device in accordance with thepresent embodiment is configured to encode, for each QP encoding unitregion, an index indicating a QP difference value as explained in FirstEmbodiment, instead of encoding the QP difference value regarding onlyone CU belonging to the QP encoding unit region. Moreover, as with FirstEmbodiment, the video encoding device in accordance with the presentembodiment is configured to encode a transform rule index of a transformrule that indicates a relation between a QP difference value and anindex, as explained in First Embodiment.

The following details the video encoding device in accordance with thepresent embodiment with reference to drawings.

Initially, an explanation is made as to a configuration of a videoencoding device 114 in accordance with the present embodiment, withreference to FIG. 36. FIG. 36 is a block diagram showing a configurationof the video encoding device 114. As shown in FIG. 36, the videoencoding device 114 includes a side information determination section1141, a side information encoding section 1142, a CU setting section 43,a CU encoding section 44, a variable-length code multiplexing section25, a CU decoding section 46, and a frame memory 27.

The side information determination section 1141 determines sideinformation in accordance with an input image #100, and outputs thedetermined side information as side information #1141. The sideinformation #1141 includes pieces of information such as (i) a pictureparameter set which is a set of parameters regarding the input image#100, (ii) a slice header which is header information with respect toeach of slices included in the input image #100, (iii) CU informationwhich is a set of parameters with respect to each of CUs included in aslice, and (iv) TU information which is a set of parameters with respectto each of TUs included in a CU.

Specifically, the side information determination section 1141 determinesthe (longitudinal and lateral) size of a QP encoding unit region inaccordance with a predetermined algorithm with respect to each slice (oreach picture), and causes size information indicative of the size of theQP encoding unit region to be stored in a slice header (pictureparameter set) of the side information #1141.

Furthermore, the side information determination section 1141 determines,with respect to each slice, a set of QP difference values for limitingQP values assignable to CUs included in the slice. That is, QP valuesassignable to CUs included in the slice are limited so that a QPdifference value between each of the QP values and a QP value assignedto an immediately preceding CU included in the same slice is included inthe set of the QP difference values. Furthermore, the side informationdetermination section 1141 determines, with respect to each slice, atransform rule regarding the slice, and incorporates a transform ruleindex for identifying the transform rule into a corresponding sliceheader.

Furthermore, the side information determination section 1141 defines aQP encoding unit region constituting the input image #100 (or eachslice) in accordance with size information for the QP encoding unitregion in the picture parameter set (or slice header). Further, withrespect to only one CU (selection target CU) selected for each QPencoding unit region, the side information determination section 1141transforms a QP difference value (qp_delta) into an index(qp_delta_index) with reference to a QP difference value table. Then,the side information determination section 1141 (i) outputs, to the sideinformation encoding section 1142, the side information #1141 that is CUinformation of the selection target CU which information contains theindex and (ii) outputs the QP difference value to the CU setting section43.

The side information encoding section 1142 encodes the side information#1141 and outputs side information encoded data #1142. The sideinformation encoded data #1142 is supplied to the variable-length codemultiplexing section 25. When encoding the side information #1141, theside information encoding section 1142 encodes an index of each QPencoding unit region, the size information, and a transform rule index.To be specific, the side information encoding section 1142 encodes theindex of each QP encoding unit region into a binary sequence having alength corresponding to the sizes of an absolute value of the index.

The CU setting section 43, the CU encoding section 44, the CU decodingsection 46, the variable-length code multiplexing section 25, and theframe memory 27 have been already explained in First or SecondEmbodiment and therefore explanations thereof are omitted here.

Modification Example 1 of Video Decoding Device 113 and Video EncodingDevice 114

The above described side information determination section 1141 of thevideo encoding device 114 determines a transform rule for each slice.Alternatively, however, the side information determination section 1141may select, with respect to each slice, one transform rule frompredetermined plural kinds of transform rules.

For example, the side information determination section 1141 may (i)select any one of a transform rule represented byqp_delta=qp_delta_index, a transform rule represented byqp_delta=qp_delta_index*2 (i.e., a transform rule in which an equivalentQP difference value table is as shown in (b) of FIG. 8), and a transformrule in which an equivalent QP difference value table is as shown in (c)of FIG. 8 and (ii) cause a transform rule index indicative of thetransform rule to be stored in a slice header of the side information#1141 with reference to a transform rule table. Here, the transform ruletable is a table in which transform rules and transform rule indices areassociated with each other. The video encoding device 114 and the videodecoding device 113 have respective storage sections (not shown) inwhich a common transform rule table is stored. Examples of the transformrule table encompass a table in which (i) a transform rule index foridentifying the transform rule represented by qp_delta=qp_delta_index is0, (ii) a transform rule index for identifying the transform rulerepresented by qp_delta=qp_delta_index*2 is 1, and (iii) a transformrule index for identifying the transform rule in which an equivalent QPdifference value table is as shown in (c) of FIG. 8 is 2.

Alternatively, the side information determination section 1141 mayselect, with respect to each slice, one QP difference value table frompredetermined plural kinds of QP difference value tables.

For example, the side information determination section 1141 may (i)select a QP difference value table in which qp_delta and qp_delta_indexbecomes identical values or a QP difference value table as shown in (a)of FIG. 8 and (ii) cause a roughness-specifying flag indicative of theQP difference value table to be stored in a slice header of the sideinformation #1141 with reference to information for selecting a table.Here, the information for selecting a table is a table in which QPdifference value tables and roughness-specifying flags are associatedwith each other. The video encoding device 114 and the video decodingdevice 113 have respective storage sections (not shown) in which commoninformation for selecting a table is stored.

The video encoding device 114 and the video decoding device 113 maydefine a roughness-specifying flag, which is a binary flag indicative ofthe former QP difference value table, as “0” and define aroughness-specifying flag indicative of the latter QP difference valuetable as “1”.

In the above two examples, when decoding the side information encodeddata #1131 a, the side information decoding section 1132 of the videodecoding device 113 decodes encoded data of a transform rule index(roughness-specifying flag) of each slice header, thereby generating thetransform rule index (roughness-specifying flag) as a part of the sideinformation #1132.

With reference to a transform rule table stored in a storage section(not shown), the CU setting section 1133 specifies, from a transformrule index (roughness-specifying flag) included in a slice header of theside information #1132, arithmetic algorithm information (QP differencevalue table) indicative of a transform rule, which arithmetic algorithminformation is also stored in the storage section. Then, with respect toeach QP encoding unit region, the CU setting section 1133 transforms,based on the specified arithmetic information (QP difference valuetable), an index of a selection target CU in the QP encoding unit regionincluded in the side information #1132 into a OP difference value to beoutputted to the CU decoding section 1134.

Note that the plural kinds of QP difference value tables may be QPdifference value tables each of which is set in accordance with aprediction mode. For example, the plural kinds of QP difference valuetables may be two kinds of QP difference value tables, that is, a QPdifference value table for intra-prediction mode and a QP differencevalue table for other prediction mode. Moreover, the QP difference valuetable for intra-prediction mode may be a QP difference value table inwhich qp_delta and qp_delta_index have identical values, and the QPdifference value table for other prediction mode may be a QP differencevalue table as shown in (b) of FIG. 8.

According to the configuration, in a case where a prediction mode of theselection target CU received from a predicted image generation section(not shown) is intra-prediction mode, the side information determinationsection 1141 transforms a QP difference value of the selection target CUinto an index with reference to the former QP difference value table. Onthe other hand, in a case where a prediction mode of the selectiontarget CU received from the predicted image generation section (notshown) is other prediction mode such as an inter-prediction mode, theside information determination section 1141 transforms the QP differencevalue of the selection target CU into an index with reference to thelatter QP difference value table.

The plural kinds of QP difference value tables may be QP differencevalue tables each of which is set in accordance with a slice type. Forexample, the plural kinds of QP difference value tables may be two kindsof QP difference value tables, that is, (i) a QP difference value tablefor I slice and B slice and (ii) a QP difference value table for Pslice.

For example, the side information determination section 1141 may (i)determine a set of QP difference values with the use of the method asdescribed in First Embodiment such that a factor for the I slice and theB slice becomes 1 and (ii) generate the QP difference value table for Islice and B slice from the set of QP difference values. Similarly, theside information determination section 1141 may (i) determine a set ofQP difference values with the use of the method as described in FirstEmbodiment such that a factor for the P slice becomes 2 and (ii)generate the OP difference value table for P slice from the set of QPdifference values.

According to the configuration, in a case where the type of a slice towhich the selection target CU belongs is the I slice or the B slice, theside information determination section 1141 transforms a QP differencevalue of the selection target CU into an index with reference to theformer QP difference value table. On the other hand, in a case where thetype of a slice to which the selection target CU belongs is the P slice,the side information determination section 1141 transforms a QPdifference value of the selection target CU into an index with referenceto the latter QP difference value table.

Note that the plural kinds of arithmetic rules can be set in a mannersimilar to that of the plural kinds of QP difference value tables.

Modification Example 2 of Video Decoding Device 113 and Video EncodingDevice 114

In Fifth Embodiment, the video encoding device is explained whichdetermines whether to encode, with respect to each of LCUs constitutingan input image #100, a QP difference value per LCU or per QP encodingregion constituting an LCU, depending on whether or not adeltaQuantAvailCU flag is true.

The video encoding device 114 may determine whether to encode an index(qp_delta_index) with respect to each LCU or with respect to each QPencoding unit region constituting an LCU depending on whether or not thedeltaQuantAvailCU flag is true, as with the video encoding device inaccordance with Sixth Embodiment.

Further, the side information determination section 1141 of the videoencoding device 114 may (i) select, with respect to each selectiontarget CU, any one of plural kinds of transform rules set for respectiveslices (or LCUs or CUs) and (ii) transform a QP difference value into anindex with the use of the selected transform rule. In this case, theside information determination section 1141 causes a transform ruleindex of the selected transform rule to be stored in CU information ofthe selection target CU together with an index of the selection targetCU.

Note that, in a case where each of the plural kinds of transform rulesis set for each slice or for each LCU, the side informationdetermination section 1141 may (i) select one transform rule withrespect to each LCU and (ii) cause a transform rule index indicative ofthe selected transform rule to be included in CU information of the LCU.Similarly, in a case where each of the plural kinds of transform rulesis set for each slice, the side information determination section 1141may (i) select one transform rule with respect to each slice and (ii)cause a transform rule index indicative of the selected transform ruleto be included in the slice header.

For example, the side information determination section 1141 may beconfigured to select, for each slice, (i) a transform rule in whichqp_delta and qp_delta_index are identical values or (ii) a transformrule in which an equivalent QP difference value table is as shown in (b)of FIG. 8.

According to the configuration, (i) in a case where the side informationdetermination section 1141 determines an index (qp_delta_index) for eachLCU, the side information determination section 1141 may calculate anindex to be stored in the side information #1141 from a QP differencevalue of a selection target CU with the use of the former transformrule, and (ii) in a case where the side information determinationsection 1141 determines an index (qp_delta_index) for each QP encodingunit region, the side information determination section 1141 maycalculate an index to be stored in the side information #1141 from a QPdifference value of the selection target CU with the use of the lattertransform rule.

The video encoding device 114 may determine, with respect to each sliceconstituting the input image #100, whether to encode an index for theslice or for each LCU constituting the slice (or for each QP encodingunit region).

According to the configuration, in a case where the side informationdetermination section 1141 determines an index for each slice, the sideinformation determination section 1141 may calculate an index to bestored in the side information #1141 from a QP difference value of aselection target CU with the use of the former transform rule, and (ii)in a case where the side information determination section 1141determines an index for each LCU (or for each QP encoding unit region),the side information determination section 1141 may calculate an indexto be stored in the side information #1141 from a QP difference value ofthe selection target CU with the use of the latter transform rule.

In this case, the CU setting section 1133 of the video decoding device113 refers to, with respect to each LCU, deltaQuantAvailCU included inCU information of the LCU in the side information #1132. In a case wherea deltaQuantAvailCU flag of the LCU is “true”, the CU setting section1133 refers to CU information of each CU belonging to the LCU andcalculates a QP difference value 1133 a, from an index, with respect toa CU whose CU information includes the index with the use of a transformrule indicated by a transform rule index included in the slice header.On the other hand, in a case where the deltaQuantAvailCU flag of the LCUis “false”, the CU setting section 1133 refers to CU information of theLCU and transforms an index included in the CU information into a QPdifference value 1133 a with the use of a transform rule indicated by atransform rule index included in the slice header.

Then, the CU setting section 1133 outputs the QP difference value 1133 ato the CU decoding section 1134. The other operations are similar tothose of the video decoding device 113 in accordance with ModificationExample 1.

Note that the macroblock of First Embodiment corresponds to an LCU(Largest Coding Unit, also called root of Coding Tree) of HEVC (HighEfficiency Video Coding) that is proposed as a standard succeeding toH.264/MPEG-4 AVC. Each of the sub macroblock and the block correspondsto CU (Coding Unit, also called leaf of Coding Tree), a PU (PredictionUnit), or a TU (Transformation Unit) of HEVC.

Lastly, the following table explains variables used in the drawingsshowing the syntax.

TABLE 1 trafoDepth Variable indicative of divided node of TU IftrafoDepth = 0, TU is identical with CU If trafoDepth = 1, TU is one offour nodes obtained by dividing CU cbp_yuv_root Flag indicative ofwhether or not DCT coefficient other than 0 is included in subordinateTU node. Encoded by trafoDepth = 0 and CAVLC. no_resiual_data_flag Flagindicative of whether or not DCT coefficient other than 0 is included insubordinate TU node. Encoded by trafoDepth = 0 and CABAC.split_transform_flag TU division flag cbp_luma[trafoDpth + 1] Flagindicative of whether or not DCT transform coefficient whose luminancecomponent is not 0 is included in next node (TU node of trafoDepth + 1).Encoded by CAVLC. cbp_cb[trafoDpth + 1] Flag indicative of whether ornot DCT transform coefficient whose color difference Cb component is not0 is included in next node (TU node of trafoDepth + 1). Encoded byCAVLC. cbp_cr[trafoDpth + 1] Flag indicative of whether or not DCTtransform coefficient whose color difference Cr component is not 0 isincluded in next node (TU node of trafoDepth + 1). Encoded by CAVLC.code_block_flag_luma Flag indicative of whether or not DCT[x0][y0][trafoDepth] transform coefficient whose luminance component isnot 0 is included in current TU node (TU node of trafoDepth). Encoded byCABAC. code_block_flag_cb Flag indicative of whether or not DCT[x0][y0][trafoDepth] transform coefficient whose color difference Cbcomponent is not 0 is included in current TU node (TU node oftrafoDepth). Encoded by CABAC. code_block_flag_cr Flag indicative ofwhether or not DCT [x0][y0][trafoDepth] transform coefficient whosecolor difference Cr component is not 0 is included in current TU node(TU node of trafoDepth). Encoded by CABAC.

The present invention is not limited to the description of theembodiments above, but may be altered by a skilled person within thescope of the claims. An embodiment based on a proper combination oftechnical means disclosed in different embodiments is encompassed in thetechnical scope of the present invention.

As above described, the encoding device of the present inventionpreferably further includes information generation means for generatinginformation indicative of correspondences between the n differencevalues and the n integers, respectively, the information generated bythe information generation means being outputted to outside as encodeddata together with the binary sequence.

According to the configuration, the encoding device can cause a decodingdevice, which is capable of decoding the difference values, to decodethe difference values in a case where the binary sequence andinformation indicative of the correspondences are inputted. Moreover,the configuration of the present invention brings about a further effectof appropriately changing the correspondences between the n differencevalues and the respective n integers in accordance with an input imageto be encoded.

According to the encoding device of the present invention, it ispreferable that the n difference values are obtained by multiplying then integers with a predetermined value, and the information is thepredetermined value.

According to the configuration, the information indicative of thecorrespondences between the n difference values and the respective nintegers is expressed in a single predetermined value. Therefore, it ispossible to reduce the amount of codes of the information outputted tooutside as encoded data.

According to the encoding device of the present invention, it ispreferable that the transform means transforms one of the n differencevalues which one has i-th smallest absolute value into one of the nintegers which one has i-th smallest absolute value, and the absolutevalue of the integer is smaller than the absolute value of thedifference value.

According to the configuration, the encoding device of the presentinvention transforms a difference value regarding a unit region into aninteger having an absolute value smaller than that of the differencevalue, regardless of how the difference value is determined out of the ndifference values.

Therefore, the encoding device of the present invention brings about afurther effect of surely reducing the amount of codes of a quantizationparameter to be supplied to the decoding device.

It is preferable that the encoding device of the present inventionfurther includes calculation means for calculating a ratio of said eachof the n difference values to a group consisting of the differencebetween the quantization parameter and the predetermined reference valuein each unit region, the transform means transforming the differencevalue into the integer in such a manner that as the difference value hasthe larger ratio calculated by the calculation means, the integer has asmaller absolute value.

According to the configuration, in the encoding device of the presentinvention, the transform means transforms the difference value into theinteger in such a manner that as the difference value has the largerratio in the group consisting of the difference of each unit region, theinteger has a smaller absolute value (that is, a binary sequencegenerated from the integer becomes shorter).

Therefore, the encoding device of the present invention brings about afurther effect of more efficiently reducing the amount of codes of aquantization parameter to be supplied to the decoding device.

According to the encoding device of the present invention, it ispreferable that the input image consists of a plurality of second unitregions, and each of the plurality of second unit regions consists ofthe plurality of unit regions, the setting means sets a quantizationparameter of a specific unit region predetermined for each of theplurality of second unit regions in such a manner that a difference inquantization parameter between a pair of the specific unit region and aunit region earlier in an order of encoding is capable of being a valueother than the n difference values, and the binary sequence generationmeans generates a binary sequence having a length corresponding to anabsolute value of the difference in quantization parameter between thepair.

In general, when a region constituted by unit regions having similarimage characteristics (i.e. it is appropriate to have similarquantization parameters) is set as a second unit region (e.g. enlargedmacroblock), by setting a quantization parameter for each of unitregions in the second unit region other than a specific region (e.g.macroblock at the upper left corner of the enlarged macroblock) in sucha manner that a pair of the unit region and a unit region with anearlier encoding order than that unit region has a sufficiently smalldifference in quantization parameter, it is possible to carry outappropriate quantization.

Therefore, the encoding device of the present invention can carry outappropriate quantization even when sufficiently reducing the number n ofcandidates for a difference between quantization parameters for a pairof each of the unit regions other than specific regions and a unitregion with an earlier encoding order than that unit region in settingquantization parameters for the unit regions other than specificregions. Consequently, the encoding device of the present invention cansave a storage region for storing information in which n integers and ndifference values regarding quantization parameters are related to eachother one by one.

According to the encoding device of the present invention, it ispreferable that the encoded data includes the information in which nintegers are related to n difference values regarding quantizationparameters, respectively, and the extraction means extracts theinformation from the encoded data.

With the arrangement, the decoding device of the present invention canextract the information from the encoded data. Accordingly, the decodingdevice of the present invention is not required to store in advance theinformation in order to carry out inverse-quantization based on aquantization parameter supplied from the encoding device of the presentinvention.

According to the encoding device of the present invention, it ispreferable that the information extracted by the extraction means fromthe encoded data is a predetermined value, and the specifying meansspecifies the difference values by multiplying the integers generated bythe integer generation means with the predetermined value extracted bythe extraction means.

With the arrangement, the information included in the encoded data is apredetermined value. Accordingly, the decoding device of the presentinvention can save a storage region in which the information is storedin order to specify the difference value.

According to the encoding device of the present invention, it ispreferable that the decoded image consists of a plurality of second unitregions, and each of the second unit regions consists of the unitregions, with respect to each of unit regions which are included in aplurality of unit regions constituting the decoded image as a whole andwhich are other than specific regions predetermined respectively for thesecond unit regions, the specifying means specifying a difference valuefor said each of unit regions from an integer for said each of unitregions according to the information, and with respect to the specificunit regions, the specifying means specifies the integers generated bythe integer generation means themselves as difference values.

With the arrangement, the decoding device of the present inventionspecifies a difference value for each of the unit regions other thanspecific regions from an integer for said each of unit regions accordingto the information in which n integers and n difference values forquantization parameters are related to one by one. When the encodingdevice which supplies encoded data regards a region constituted by unitregions having similar image characteristics (i.e. it is appropriate tohave similar quantization parameters) as a second unit region (e.g.enlarged macroblock) and reduces the number n of candidates fordifference values to be determined for the unit regions other thanspecific regions, the decoding device of the present invention can savea storage region in which the information is to be stored.

Encoded data including the information in which n integers are relatedto n difference values regarding quantization parameters, respectively,is also encompassed in the scope of the present invention.

The encoding device of the present invention may be arranged such thatthe third unit region is a coding unit (CU) or a transform unit (TU).

Furthermore, the encoding device of the present invention may bearranged such that the third unit region is a CU, the unit regions areLCUs, and the encoding device further comprises second determinationmeans for determining, in accordance with a predetermined standard,whether an image in each of the LCUs is to be quantized according to thevalue of the quantization parameter calculated by the calculation means,or an image in each of CUs constituting each of the LCUs is to bequantized according to the value of the quantization parameter of saideach of CUs.

Also with the above arrangements, the encoding device of the presentinvention can reduce an amount of codes in a quantization parameter,compared with the conventional art.

It is desirable to arrange the encoding device of the present inventionsuch that the third unit region is a CU, the encoding device furthercomprises judgment means for judging whether a prediction mode for a CUfirstly selected by the selection means in each of a plurality of fourthunit regions constituting the unit region is an intra-prediction mode ornot, and the calculation means calculates a value of the quantizationparameter to be referred to when an image in each CU to be quantized ina fourth unit region for which the prediction mode is judged as anintra-prediction mode is quantized, the calculation being made based ona difference value of a quantization parameter of the CU firstlyselected in the fourth unit region instead of the difference value ofthe quantization parameter determined by the determination means withrespect to a unit region to which the fourth unit region belongs.

With the arrangement, when the prediction mode for a CU firstly selectedin each fourth unit region is an intra-prediction mode, the encodingdevice of the present invention can quantize an image in the fourth unitregion by using quantization parameters with different difference valuesbetween the fourth unit region and other fourth unit region in a unitregion to which the fourth unit region belongs.

In other words, in the encoding device of the present invention, thenumber of difference values of quantization parameters to be outputtedto a decoding device is relatively higher when the input image includesmany CUs for which the prediction mode is an intra-prediction mode thanwhen the input image includes many CUs for which the prediction mode isan inter-prediction mode.

It is known that when the input image includes many CUs for which theprediction mode is an intra-prediction mode, increasing quantizationaccuracy allows greatly reducing an amount of codes in encoded datacompared with when the input image includes many CUs for which theprediction mode is an inter-prediction mode.

Therefore, the encoding device of the present invention canappropriately reduce an amount of codes in encoded data according to aratio of a CU in the input image for which the prediction mode is anintra-prediction mode to a CU for which the prediction mode is aninter-prediction mode.

It is desirable to arrange the encoding device of the present inventionso as to further include: judgment means for judging a slice type ofeach of a plurality of slices constituting the input image; and unitregion setting means for setting sizes of unit regions constituting eachof the plurality of slices to sizes according to the slice type judgedby the judgment means.

With the arrangement, the encoding device of the present invention canreduce an amount of codes in encoded data by appropriately setting thesize of a unit region to be quantized using quantization parameters withthe same difference value, according to the slice type of a slice towhich the unit region belongs.

It is desirable to arrange the encoding device of the present inventionso as to further include: transform means for transforming thedifference value determined by the determination means with respect toeach unit region into a corresponding integer in accordance with atransform rule by which the difference value of the quantizationparameter is related to an integer one by one so as to provide n sets ofthe difference value of the quantization parameter and the integer; andbinary sequence generation means for generating a binary sequence havinga length corresponding to a size of an absolute value of the integerobtained by transform by the transform means, a total of absolute valuesof n number of the integer being smaller than a total of absolute valuesof n number of the difference value.

With the arrangement, the encoding device of the present inventiontransforms the absolute values of integers transformed from differencevalues of quantization parameters into binary sequences. The total ofabsolute values of n number of the integer is smaller than the total ofabsolute values of n number of the difference value. Therefore, it isoften that the total of the lengths of the binary sequences as a resultof the above transform is statistically smaller than the total of thelengths of binary sequences to which absolute values of differencevalues of quantization parameters have been transformed.

Therefore, the encoding device of the present invention can reduce anamount of codes in a difference value of a quantization parameter.

Furthermore, the decoding device of the present invention may bearranged such that the third unit region is a coding unit (CU) or atransform unit (TU).

Furthermore, the decoding device of the present invention may bearranged such that the third unit region is a CU, the unit regions areLCUs, and the decoding device further comprises determination means fordetermining, in accordance with a predetermined standard, whether aquantization image in each of the LCUs is to be inverse-quantizedaccording to the value of the quantization parameter specified by thespecifying means, or a quantization image in each of CUs constitutingeach of the LCUs is to be inverse-quantized according to the value ofthe quantization parameter of said each of CUs.

Also with the above arrangements, the decoding device of the presentinvention can specify, with a smaller load, quantization parameters tobe used in inverse-quantization.

It is desirable to arrange the decoding device of the present inventionsuch that the third unit region is a CU, the encoding device furthercomprises judgment means for judging whether a prediction mode for a CUfirstly selected by the selection means in each of a plurality of fourthunit regions constituting the unit region is an intra-prediction mode ornot, and the specifying means specifies a value of the quantizationparameter to be referred to when a quantization image in each CU to beinverse-quantized in a fourth unit region for which the prediction modeis judged as an intra-prediction mode is quantized, the specifying beingmade based on a difference value of a quantization parameter of the CUfirstly selected in the fourth unit region instead of the differencevalue of the quantization parameter read out by the reading means withrespect to a unit region to which the fourth unit region belongs.

With the arrangement, the encoding device of the present invention cangenerate a decoded image by decoding encoded data with a smaller amountof codes which is transmitted from the encoding device of the presentinvention including judgment means for judging whether a prediction modefor each CU is an intra-prediction mode or not.

It is desirable to arrange the decoding device of the present inventionso as to further include: judgment means for judging a slice type ofeach of a plurality of slices constituting the input image; and unitregion setting means for setting sizes of unit regions constituting eachof the plurality of slices to sizes according to the slice type judgedby the judgment means.

With the arrangement, the decoding device of the present invention cangenerate a decoded image by decoding encoded data transmitted from theencoding device of the present invention having similar judgment means.

It is desirable to arrange the decoding device of the present inventionsuch that the reading means reads out, instead of the difference valueof the quantization parameter, an integer corresponding to thedifference value from the encoded data, the decoding device furthercomprises: transform means for transforming the integer read out by thereading means with respect to each unit region into a correspondingdifference value in accordance with a transform rule by which thedifference value of the quantization parameter is related to the integerone by one so as to provide n sets of the difference value of thequantization parameter and the integer; and the specifying meansspecifies a value of the quantization parameter to be referred to wheninverse-quantizing a quantization image in each of the third unitregions to be inverse-quantized in each of the unit regions, thespecifying being made based on the difference value of the quantizationparameter obtained by the transform means transforming the integer readout by the reading means in the unit region, and a total of absolutevalues of n number of the integer is smaller than a total of absolutevalues of n number of the difference value.

With the arrangement, the decoding device of the present invention cangenerate a decoded image by decoding encoded data transmitted from theencoding device of the present invention having transform means fortransforming a difference value of a quantization parameter into aninteger by the transform rule.

INDUSTRIAL APPLICABILITY

The present invention is preferably applicable to an encoding device forencoding an image to generate encoded data, and to a decoding device fordecoding encoded data generated by such an encoding device.

REFERENCE SIGNS LIST

-   1 Video decoding device (decoding device)-   11 Variable-length code inverse-multiplexing section-   12 Side information decoding section (extraction means, specifying    means)-   13 MB setting section (specifying means)-   14 MB decoding section-   15 Frame memory-   2 Video encoding device (encoding device)-   21 Side information determination section (setting means, transform    means, calculation means)-   22 Side information encoding section (binary sequence generation    means)-   23 MB setting section-   24 MB encoding section-   25 Variable-length code multiplexing section-   26 MB decoding section-   27 Frame memory-   3 Video decoding device-   31 Variable-length code inverse-multiplexing section-   32 Side information decoding section (selection means, reading    means)-   33 CU setting section-   34 CU decoding section (specifying means)-   4 Video encoding device-   41 Side information determination section (selection means,    determination means)-   42 Side information encoding section-   43 CU setting section-   44 CU encoding section (calculation means)-   46 CU decoding section-   7 Video decoding device-   74 CU decoding section (judgment means)-   8 Video encoding device-   81 Side information determination section (determination means)-   9 Video decoding device-   92 Side information decoding section (determination means)-   10 Video decoding device-   101 Side information determination section (second determination    means)-   111 Video decoding device-   1112 Side information decoding section (judgment means, unit region    setting means)-   112 Video encoding device-   1121 Side information determination section (judgment means, unit    region setting means)-   113 Video decoding device-   1133 CU setting section (reading means, transform means)-   114 Video encoding device-   1141 Side information determination section (transform means)-   1142 Side information encoding section (binary sequence generation    means)

1. An encoding device for quantizing, in accordance with a value of aquantization parameter, an image in each of a plurality of unit regionsconstituting an input image to be encoded, the encoding devicecomprising: setting means for setting a quantization parameter used inencoding each unit region, the setting means setting an quantizationparameter for each unit region in such a manner that a differencebetween a quantization parameter for a unit region and a predeterminedreference value is equal to one of n predetermined difference values;transform means for transforming, with respect to each unit region, thedifference between the quantization parameter for the unit region andthe predetermined reference value into an integer in accordance with atransform rule by which the n difference values are transformed into nnumber of integers, respectively; and binary sequence generation meansfor generating a binary sequence having a length corresponding to a sizeof an absolute value of the integer into which the difference istransformed by the transform means, a total of absolute values of the nintegers being smaller than a total of absolute values of the ndifference values.
 2. The encoding device as set forth in claim 1,further comprising information generation means for generatinginformation indicative of correspondences between the n differencevalues and the n integers, respectively, the information generated bythe information generation means being outputted to outside as encodeddata together with the binary sequence.
 3. The encoding device as setforth in claim 2, wherein the n difference values are obtained bymultiplying the n integers with a predetermined value, and theinformation is the predetermined value.
 4. The encoding device as setforth in claim 1, wherein the transform means transforms one of the ndifference values which one has i-th smallest absolute value into one ofthe n integers which one has i-th smallest absolute value, and theabsolute value of the integer is smaller than the absolute value of thedifference value.
 5. The encoding device as set forth in Claim 1,further comprising calculation means for calculating a ratio of saideach of the n difference values to a group consisting of the differencebetween the quantization parameter and the predetermined reference valuein each unit region, the transform means transforming the differencevalue into the integer in such a manner that as the difference value hasthe larger ratio calculated by the calculation means, the integer has asmaller absolute value.
 6. The encoding device as set forth in claim 1,wherein the input image consists of a plurality of second unit regions,and each of the plurality of second unit regions consists of theplurality of unit regions, the setting means sets a quantizationparameter of a specific unit region predetermined for each of theplurality of second unit regions in such a manner that a difference inquantization parameter between a pair of the specific unit region and aunit region earlier in an order of encoding is capable of being a valueother than the n difference values, and the binary sequence generationmeans generates a binary sequence having a length corresponding to anabsolute value of the difference in quantization parameter between thepair.
 7. A decoding device for decoding encoded data to set quantizationparameters regarding unit regions constituting a decoded image, thedecoding device comprising: extraction means for extracting data ofbinary sequences regarding the unit regions from the encoded data;integer generation means for generating integers corresponding tolengths of the binary sequences regarding the unit regions from the dataof binary sequences extracted by the extraction means; and specifyingmeans for specifying, according to information in which n integers arerelated to n difference values regarding quantization parameters,respectively, difference values for the unit regions based on integersfor the unit regions that are generated by the integer generation means,the quantization parameters for the unit regions being generated basedon the difference values specified by the specifying means.
 8. Thedecoding device as set forth in claim 7, wherein the encoded dataincludes the information in which n integers are related to n differencevalues regarding quantization parameters, respectively, and theextraction means extracts the information from the encoded data.
 9. Thedecoding device as set forth in claim 8, wherein The informationextracted by the extraction means from the encoded data is apredetermined value, and the specifying means specifies the differencevalues by multiplying the integers generated by the integer generationmeans with the predetermined value extracted by the extraction means.10. The decoding device as set forth in claim 7, wherein the decodedimage consists of a plurality of second unit regions, and each of thesecond unit regions consists of the unit regions, with respect to eachof unit regions which are included in a plurality of unit regionsconstituting the decoded image as a whole and which are other thanspecific regions predetermined respectively for the second unit regions,the specifying means specifying a difference value for said each of unitregions from an integer for said each of unit regions according to theinformation, and with respect to the specific unit regions, thespecifying means specifies the integers generated by the integergeneration means themselves as difference values.
 11. Encoded dataoutputted by an encoding device as set forth in claim 2, including theinformation in which n integers are related to n difference valuesregarding quantization parameters, respectively. 12-17. (canceled)
 18. Adecoding device for decoding encoded data to set quantization parametersregarding unit regions constituting a decoded image, the decoding devicecomprising: selection means for selecting, in a predetermined order, aplurality of third unit regions constituting each of the unit regionsconstituting the decoded image; reading means for reading, from theencoded data, a difference value of a quantization parameter for one ofthird unit regions to be inverse-quantized in each of the unit regionsconstituting the decoded image, said one of third unit regions beingfirstly selected by the selection means; and specifying means forspecifying a value of the quantization parameter to be referred to whena quantization image in each third unit region to be inverse-quantizedin each of the unit regions constituting the decoded image, thespecifying being made based on the difference value of the quantizationparameter read out in said each of the unit regions by the readingmeans.
 19. The decoding device as set forth in claim 18, wherein thethird unit region is a coding unit (CU) or a transform unit (TU). 20.The decoding device as set forth in claim 19, wherein the third unitregion is a CU, the unit regions are LCUs, and the decoding devicefurther comprises determination means for determining, in accordancewith a predetermined standard, whether a quantization image in each ofthe LCUs is to be inverse-quantized according to the value of thequantization parameter specified by the specifying means, or aquantization image in each of CUs constituting each of the LCUs is to beinverse-quantized according to the value of the quantization parameterof said each of CUs.
 21. The decoding device as set forth in claim 18,wherein the third unit region is a CU, the encoding device furthercomprises judgment means for judging whether a prediction mode for a CUfirstly selected by the selection means in each of a plurality of fourthunit regions constituting the unit region is an intra-prediction mode ornot, and the specifying means specifies a value of the quantizationparameter to be referred to when a quantization image in each CU to beinverse-quantized in a fourth unit region for which the prediction modeis judged as an intra-prediction mode is quantized, the specifying beingmade based on a difference value of a quantization parameter of the CUfirstly selected in the fourth unit region instead of the differencevalue of the quantization parameter read out by the reading means withrespect to a unit region to which the fourth unit region belongs. 22.The decoding device as set forth in claim 18, further comprising:judgment means for judging a slice type of each of a plurality of slicesconstituting the input image; and unit region setting means for settingsizes of unit regions constituting each of the plurality of slices tosizes according to the slice type judged by the judgment means.
 23. Thedecoding device as set forth in claim 18, wherein the reading meansreads out, instead of the difference value of the quantizationparameter, an integer corresponding to the difference value from theencoded data, the decoding device further comprises: transform means fortransforming the integer read out by the reading means with respect toeach unit region into a corresponding difference value in accordancewith a transform rule by which the difference value of the quantizationparameter is related to the integer one by one so as to provide n setsof the difference value of the quantization parameter and the integer;and the specifying means specifies a value of the quantization parameterto be referred to when inverse-quantizing a quantization image in eachof the third unit regions to be inverse-quantized in each of the unitregions, the specifying being made based on the difference value of thequantization parameter obtained by the transform means transforming theinteger read out by the reading means in the unit region, and a total ofabsolute values of n number of the integer is smaller than a total ofabsolute values of n number of the difference value.